Tag Archives: Nature Communications

Arnica diversifolia

Botanical Name : Arnica diversifolia
Family: Asteraceae
Tribe: Heliantheae
Genus: Arnica
Species: A. ovata
Kingdom: Plantae
Order: Asterales

Synonyms:
*Arnica diversifolia Greene
*Arnica latifolia var. viscidula

Common Names: Rayless arnica

Other Names: Sticky leaf arnica,Arnica ovata

Habitat ; Arnica diversifolia is native to western Canada (Yukon, Alberta, British Columbia), and the western United States (Alaska, Washin

gton, Oregon, California, Nevada, Utah, Idaho, Montana, Wyoming, Colorado). It grows on rocky places from moderate to high elevations in mountains

Description:
Arnica diversifolia is a perennial herb growing 6–24 inches. Erect. Stems 1 to several, unbranched, with sticky gland-bearing hairs. Leaves triangular, irregularly toothed; 3–4 pairs along stem, with largest pair 1–3 in. long and in the middle. Lower leaves on petioles; upper leaves sessile. Flower heads 1–5 in cluster, 8–13 ray flowers less than 1 in. long in head. Flower heads are yellow, with both ray florets and disc florets.
Flowering Time: All Summer

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The flowers are hermaphrodite (have both male and female organs) and are pollinated by Apomictic, insects.The plant is self-fertile.
Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: acid and neutral soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist soil.

 Cultivation:
We have very little information on this species and do not know if it will be hardy in Britain, though judging by its native range it should succeed outdoors in most parts of this country. This is a convenient name for a complex of apparent hybrids involving A. mollis or A. amplexicaulis with A. cordifolia or A. latifolia. The following notes are based on the general needs of the genus. Prefers a moist, well-drained humus rich soil, preferably lime-free. Prefers a mixture of sand, loam and peat.

Propagation:
Seed – sow early spring in a cold frame. Only just cover the seed and make sure that the compost does not dry out. When large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse or cold frame for their first winter. Plant out in late spring or early summer. Division in spring

Medicinal Uses:
Antiecchymotic, antiphlogistic, nervine, sternutatory, vulnerary.

Other Uses : This plant is used as a hair conditioner. No further details are found.

Known Hazards: The whole plant is toxic and should only be used for external applications to unbroken skin[

Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.
Resources:
https://en.wikipedia.org/wiki/Arnica_ovata
http://www.pnwflowers.com/flower/arnica-diversifolia
http://www.pfaf.org/user/Plant.aspx?LatinName=Arnica+diversifolia

Picea engelmannii

Botanical Name: Picea engelmannii
Family: Pinaceae
Genus: Picea
Species: P. engelmannii
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales

Common Names : Engelmann spruce, White spruce, Mountain spruce, Silver spruce

Habitat :Picea engelmannii is native to Western N. America – Alberta and British Columbia to Arizona and New Mexico. It grows on montane regions to the tree-line, especially by swamps. Often found on poor thin rocky soils, though the best specimens are growing in deep well-drained clay-loam soils.

Description:
Picea engelmannii is a medium-sized to large evergreen tree growing to 25 metres (82 ft) – 40 metres (130 ft) tall, exceptionally to 65 metres (213 ft) tall, and with a trunk diameter of up to 1.5 metres (4.9 ft). The bark is thin and scaly, flaking off in small circular plates 5–10 cm across. The crown is narrow conic in young trees, becoming cylindric in older trees. The shoots are buff-brown to orange-brown, usually densely pubescent, and with prominent pulvini. The leaves are needle-like, 15–30 mm long, rhombic in cross-section, glaucous blue-green above with several thin lines of stomata, and blue-white below with two broad bands of stomata.

The cones are pendulous, slender cylindrical, 4–8 cm long and 1.5 cm broad when closed, opening to 3 cm broad. They have thin, flexible scales 15–20 mm long, with a wavy margin. They are reddish to dark purple, maturing pale brown 4–7 months after pollination. The seeds are black, 2–3 mm long, with a slender, 5–8 mm long pale brown wing.

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It is not frost tender. It is in leaf 12-Jan, and the seeds ripen in September. The flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and are pollinated by Wind.Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and can grow in nutritionally poor soil. Suitable pH: acid and neutral soils and can grow in very acid soils.

It cannot grow in the shade. It prefers moist or wet soil. The plant can tolerates strong winds but not maritime exposure.
It cannot tolerate atmospheric pollution.

Cultivation:
Likes abundant moisture at the roots, if grown in drier areas it must be given a deep moist soil. Tolerates poor peaty soils. Succeeds in wet cold and shallow soils but is not very wind-firm in shallow soils. Prefers a pH between 4 to 6. Dislikes shade. Intolerant of atmospheric pollution. Resists wind exposure to some degree. Plants have a shallow root system and are easily wind-blown. Often planted for its timber in N. Europe. Trees are of moderate growth after a slow start, older trees often averaging over 40cm a year. Trees grow better and faster in the north of Britain than in the south. This is not an easy tree to grow in Britain, it prefers a continental climate and, although the dormant tree is very cold hardy, the new growth in spring is very susceptible to damage by late frosts in this country. Quite long-lived in its native range, with specimens 500 – 600 years old. Seed production commences around the age of 20 – 25 years, with excellent crops every 2 – 6 years. Closely related to P. glauca, this species also hybridizes with P sitchensis in the south of its range. Plants are strongly outbreeding, self-fertilized seed usually grows poorly. They hybridize freely with other members of this genus. Trees should be planted into their permanent positions when they are quite small, between 30 and 90cm. Larger trees will check badly and hardly put on any growth for several years. This also badly affects root development and wind resistance. In some upland areas, especially over granitic or other base-poor soils, growth rate and health have been seriously affected by aluminium poisoning induced by acid rain. The crushed foliage is often said to be foetid but after the first sniff the scent is sweet and like menthol or camphor. Plants are susceptible to damage by the green spruce aphid.
Propagation:
Seed – stratification will probably improve germination so sow fresh seed in the autumn in a cold frame if possible. Sow stored seed as early in the year as possible in a cold frame. A position in light shade is probably best[78]. Seed should not be allowed to dry out and should be stored in a cool place[80]. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse or cold frame for their first winter. They can be planted out into their permanent positions in early summer of the following year, or be placed in an outdoor nursery bed for a year or so to increase in size. They might need protection from spring frosts. Cuttings of semi-ripe terminal shoots, 5 – 8cm long, August in a frame. Protect from frost. Forms roots in the spring. Cuttings of mature terminal shoots, 5 – 10cm long, September/October in a cold frame. Takes 12 months. Cuttings of soft to semi-ripe wood, early summer in a frame. Slow but sure.

Edible Uses:
Young male catkins – raw or cooked. Used as a flavouring. Immature female cones – cooked. The central portion, when roasted, is sweet and syrupy. The cones are about 5cm long. Inner bark – dried, ground into a powder and then used as a thickener in soups etc or added to cereals when making bread. An emergency food when all else fails. Seed – raw. The seed is about 2 – 4mm long and is too small and fiddly to be worthwhile unless you are desperate. A refreshing tea, rich in vitamin C, can be made from the young shoot tips.
Medicinal Uses:
An infusion of the bark has been used in the treatment of respiratory complaints, TB etc. A decoction of the leaves and gum has been used in the treatment of cancer. It was said that if this treatment did not work then nothing would work. The decoction was also used in the treatment of coughs. The ashes of the twigs, mixed with oil, have been used as an ointment or salve on damaged skin. The pitch obtained from the trunk has been used in the treatment of eczema.

Other Uses
Basketry; Charcoal; Fibre; Fuel; Tannin; Wood.

The bark is a source of tannin. The branches and the roots have been shredded, pounded and used to make cord and rope. (It is probably the bark that was used.) The bark has been used to make baskets and various small utensils. Wood – close-grained, light, soft, not strong. It is used for lumber, construction, fuel and charcoal. It is also valued for its use in the pulp industry to make paper

Engelmann spruce is of economic importance for its wood, harvested for paper-making and general construction. Wood from slow-grown trees at high altitude has a specialised use in making musical instruments such as acoustic guitars, harps, violins, and pianos. It is also used to a small extent as a Christmas tree.
Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.
Resources:
https://en.wikipedia.org/wiki/Picea_engelmannii
http://www.pfaf.org/user/Plant.aspx?LatinName=Picea+engelmannii

Astragalus gummifer

 

Botanical Name: Astragalus gummifer
Family: Fabaceae
Genus: Astragalus
Species: A. gummifer
Kingdom: Plantae
Order: Fabales

Synonyms: Gum Tragacanth. Syrian Tragacanth. Gum Dragon (known in commerce as Syrian Tragacanth).

Common Names:Tragacanth, Gum tragacanth milkvetch
Habitat: Astragalus gummifer is native to temperate regions of Western Asia centralized in Iraq, Kurdistan, Iran, Lebanon, Syria, and Turkey but also found in Afghanistan, Pakistan, and Russia. It finds dry sub-alpine slopes and valleys habitable typically 1200–2600 metres below the tree line in Iraq. The shrub grows in highlands and deserts. The shrub tolerates a pH range between 3.2 and 7.8 and temperatures as low as -5 to -10 Celsius. Standard environment consists of low water supply, full sun, no shade, and well-drained sandy/loamy soil. The plant adheres to a perennial life cycle (living for more than two years) and is an evergreen retaining its leaves throughout all seasons. Plant also known to have symbiotic relationship with soil bacteria, which fix nitrogen used by the plant.

Description:
Astragalus gummifer is an evergreen Shrub growing to 0.3 m (1ft) by 0.3 m (1ft in). The flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees, lepidoptera.It can fix Nitrogen. It is a small branching thorny shrub, the stem of which exudes a gum, vertical slits giving flat ribbon-shaped pieces and punctures giving tears; these have a horny appearance, are nearly colourless or faintly yellow, marked with numerous concentric ridges; the flakes break with a short fracture, are odourless and nearly tasteless; soaked in cold water, they swell and form a gelatinous mass 8 or 10 per cent only dissolving. This species is shrubby, with small branches and short woody gray stem surrounded by thorns. The compound leaves are stipulate with elliptical leaflets (pinnae) borne in opposite pairs. The rachis of the leaf is extended into a sharp thorn…...CLICK & SEE THE PICTURES

Cultivation:
Requires a dry well-drained soil in a sunny position. Succeeds in poor soils. Tolerates a pH in the range 3.2 to 7.8. This species is not hardy in the colder areas of the country, it tolerates temperatures down to between -5 and -10°c. Whilst it is likely to tolerate low temperatures it may not be so happy with a wet winter. Plants are intolerant of root disturbance and are best planted in their final positions whilst still small. This plant is a sub-shrub and although it produces woody stems these tend to die back almost to the base each winter. This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby. Many members of this genus can be difficult to grow, this may be due partly to a lack of their specific bacterial associations in the soil.

Propagation:
Seed – best sown as soon as it is ripe in a cold frame. A period of cold stratification may help stored seed to germinate. Stored seed, and perhaps also fresh seed, should be pre-soaked for 24 hours in hot water before sowing – but make sure that you do not cook the seed. Any seed that does not swell should be carefully pricked with a needle, taking care not to damage the embryo, and re-soaked for a further 24 hours. Germination can be slow and erratic but is usually within 4 – 9 weeks or more at 13°c if the seed is treated or sown fresh. As soon as it is large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter, planting them out into their permanent positions in late spring or early summer, after the last expected frosts.

Edible Uses:
Dried sap containing gum can be extracted from the plants root and stem, and used as a food additive mainly a thickener for salad dressings and sauces. The gum is also an excellent emulsifier and can be used in ice cream to provide its texture.

Part Used: Gummy exudation.

Constituents: The portion soluble in water contains chiefly polyarabinan-trigalaetangeddic acid; the insoluble part is called bassorin. Tragacanth also contains water, traces of starch, cellulose, and nitrogenous substances, yielding about 3 per cent ash.

Medicinal Uses:
The gum obtained from the roots and stem of the plant also bears many medicinal properties and is often referred to as tragacanth gum. The gum acts as a demulcent, which soothes irritated tissues making it helpful in treating burns. The gum acts as an antitumor as well stimulating the immune system in order to treat cancer. The plant also serves as an adaptogen fighting against chronic degenerative diseases by helping the body get to normal stress levels.

Demulcent, but owing to its incomplete solubility is not often used internally. It is much used for the suspension of heavy, insoluble powders to impart consistence to lozenges, being superior to gum arabic, also in making emulsions, mucilago, etc. Mucilage of Tragacanth has been used as anapplication to burns; it is also employed by manufacturers for stiffening calico, crape, etc.

Other Uses:
Tragacanth gum works as a thickening agent for several dyes, dressing fabrics, glues, watercolors, and ink as well as a binding agent in paper making and lozenges. Incense can be derived from the burning of the stems or gum.

Known Hazards: Many members of this genus contain toxic glycosides. All species with edible seedpods can be distinguished by their fleshy round or oval seedpod that looks somewhat like a greengage. A number of species can also accumulate toxic levels of selenium when grown in soils that are relatively rich in that element

Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider

Resources:
https://en.wikipedia.org/wiki/Astragalus_gummifer
http://www.botanical.com/botanical/mgmh/t/tragac26.html
http://www.pfaf.org/user/Plant.aspx?LatinName=Astragalus+gummifer

Araroba

Botanical Name:  Andira araroba
Family:Fabaceae/ Leguminosae
Subfamily:Faboideae
Genus:    Andira
Kingdom:    Plantae
Order:Fabales

Synonyms:  Goa Powder. Crude Chrysarobin. Bahia Powder. Brazil Powder. Ringworm Powder. Chrysatobine. Goa. Araroba Powder. Voucapoua Araroba,Vataireopsis araroba
Common Name :  Araroba
Habitat :  Andira araroba is  commonly found in Bahia, Brazil.

Description:
Andira Araroba, is large, smooth, and quite . It is met with in great abundance in certain forests in the province of Bahia, preferring as a rule low and humid spots. The tree is from 80 to 100 ft. high and has large imparipinnate leaves, the leaflets of which are oblong, about 12 in. long and 1 in. broad, and somewhat truncate at the apex. The flowers are papilionaceous, of a purple color and arranged in panicles.

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The yellowish wood has longitudinal canals and interspaces in which the powder is deposited in increasing quantity as the tree ages. It is probably due to a pathological condition. It is scraped out with an axe, after felling, sawing, and splitting the trunk, and is thus inevitably mixed with splinters and debris, so that it needs sifting, and is sometimes ground, dried, boiled, and filtered.
It irritates the eyes and face of the woodmen.

As it darkens quickly, the crude chrysarobin is changed from primrose yellow to shades of dark brown before it is met with in commerce, when it often contains a large percentage of water, added to prevent the dust from rising.

An amber skin-varnish is made with 20 parts of amber to 1 of chrysarobin in turpentine.

Chemical Composition:  Araroba is remarkable for occasionally yielding from 80 to 85 per cent of chrysophanic acid, as shown by Attfield, in 1875, and, according to the same authority, the remainder of the powder examined consists of 7 per cent of a glucoside and bitter matter, 2 of a resinous substance, 5 ½ of a red woody fiber, and ½ per cent of ash. The ashes consist chiefly of silicate of aluminum, and sulphates of potassium and of sodium. Prof J. U. Lloyd examined several specimens upon the market, and, in all cases, obtained a much smaller proportion of chrysophanic acid than stated by Mr. Attfield. Therefore, he concluded that Attfield must have procured an unexceptionally rich specimen of araroba, or that which reached this country was very inferior. Araroba readily yields chrysophanic acid to benzin. When heated in a suitable vessel, a sublimate is obtained, which, doubtless, consists largely of the aforementioned acid, as it is colored red by alkalies in solution. Araroba is chiefly employed for the preparation of chrysophanic acid (which see). Liebermann and Siedler, are authority for the statement that chrysophanic acid does not exist ready-formed in araroba, but is formed by oxidation of a natural constituent, to which they give the formula C30H26O7, and the name Chrysarobin (previously applied to araroba).

The powder is insoluble in water, but yields up to 80 per cent. of its weight to solutions of caustic alkalies and to benzene. It contains 80 to 84 per cent. of chrysarobin (easily convertible into chrysophanic acid), resin, woody fibre, and bitter extractive. Goa Powder is usually regarded as crude chrysarobin, while the purified chrysarobin, or Araroba, is a mixture extracted by hot benzene, which melts when heated, and leaves not more than 1 per cent. of ash when it finally burns.

Chrysarobin is a reduced quinone, and chrysophanic acid (also found in rhubarb yellow lichen, Buckthorn Berries, Rumox Eckolianus, a South African dock, etc., etc.), is a dioxymethylanthraquinone.

Chrysarobin contains at least five substances, and owes its power to one of these, chrysophanol-anthranol.

Lenirobin, a tetracetate,, and eurobin, a triacetate, are recommended as substitutes for chrysarobin, as they do not stain linen indelibly. (Benzin helps to remove the stains of chrysarobin.)

The action of chrysarobin on the skin is not due to germicidal properties, but to its chemical affinity for the keratin elements of the skin. The oxygen for its oxidation is abstracted from the epithelium by the drug.

Oxidized chrysarobin, obtained by boiling chrysarobin in water with sodium peroxide, can be used as an ointment for forms of eczema which chrysarobin would irritate too much.

Medicinal Uses:
The internal dose in pill or powder is a gastro-intestinal irritant, producing large, watery stools and vomiting. It is used in eczema, psoriasis, aene, and other skin diseases.

In India and South Ameriea it has been esteemed for many years for ringworm, psoriasis, dhobi’s itch, etc., as ointment, or simply moistened with vinegar or saliva. The application causes the eruption to become whitish, while the skin around it is stained dark.

In the crude form it should never be applied to the head, as it may cause erythema and oedema of the face. The 2 per cent. ointment is good in ecezema (after exudation has ceased), fissured nipples, and tylosis of the palms and soles after the skin has been removed by salicylic acid plaster, etc.

A drachm of chrysarobin may be dissolved in a fluid ounce of official flexible collodion, painted over the parts with a camel’s-hair brush, and the part coated with plain collodion to avoid staining the clothing; or chrysarobin may be dissolved in chloroform and the solution painted on the skin. For haemorrhoids, an ointment mixed with iodoform, belladonna, and petrolatum is recommended.

It is said to have been used as a taenifuge.

Known Hazards:
Precautions – Adverse reactions
The drug is severely irritating to skin and mucous membranes (redness, swelling, pustules and conjunctivitis, even without eye contact).
External administration on large skin areas could cause resorptive poisonings.
Internal administration leads to vomiting, diarrhea and kidney inflammation (with as little as
0.01 g).

Disclaimer : The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplement, it is always advisable to consult with your own health care provider.

Resources:
http://www.botanical.com/botanical/mgmh/a/araro052.html
http://www.henriettes-herb.com/eclectic/kings/andira-arar.html
http://en.wikipedia.org/wiki/Araroba_powder
http://www.globalhealth.it/xwp1/piante-medicinali/andira-araroba/

 

Photodynamic therapy

Description:
Photodynamic therapy (PDT), sometimes called photochemotherapy, is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells (phototoxicity). PDT has proven ability to kill microbial cells, including bacteria, fungi and viruses. PDT is popularly used in treating acne. It is used clinically to treat a wide range of medical conditions, including wet age-related macular degeneration and malignant cancers, and is recognised as a treatment strategy which is both minimally invasive and minimally toxic.

CLICK & SEE THE PICTURES

Most modern PDT applications involve three key components: a photosensitizer, a light source and tissue oxygen. The combination of these three components leads to the chemical destruction of any tissues which have either selectively taken up the photosensitizer or have been locally exposed to light. The wavelength of the light source needs to be appropriate for exciting the photosensitizer to produce reactive oxygen species. These reactive oxygen species generated through PDT are free radicals (Type I PDT) generated through electron abstraction or transfer from a substrate molecule and highly reactive state of oxygen known as singlet oxygen (Type II PDT). In understanding the mechanism of PDT it is important to distinguish it from other light-based and laser therapies such as laser wound healing and rejuvenation, or intense pulsed light hair removal, which do not require a photosensitizer.

Why it is done:
Photodynamic therapy (PDT) was first used in 1905 for the treatment of skin cancers. Since then, it has been further developed and used for the treatment of many kinds of cancers (lung, colon, etc.) as well as certain kinds of blindness. PDT combines a drug (called a photosensitizer) that is preferentially absorbed by certain kinds of cells and a special light source. When used together, the photosensitizer and the light destroy the targeted cells. More recently, however, PDT has been used for photorejuvenation, wrinkles, discoloration, visible veins, and acne. When used for these conditions, the photosensitizer is applied to the face and then the skin is exposed to a light source. Rapidly growing cells, oil glands, and other structures in the skin absorb the photosensitizer and are destroyed by a reaction caused by the light. Cosmetic improvement in wrinkling, age spots, and visible veins has been documented after PDT treatment.

It is a new advance in facial rejuvenation and there are currently different methods in use. For example some physicians use blue light, red light, or intense pulse light. The photosensitizer is applied to the skin and is left on for a variable period of time. The skin is then exposed to the light source and the photosensitizer is then removed. Reported side effects include transient burning, stinging, swelling, and redness. Side effects are variable depending on what is being treated, how long the photosensitizer is left on, and which light source is used. No long-term studies have been performed to evaluate long term side effects.
Procedure:
In order to achieve the selective destruction of the target area using PDT while leaving normal tissues untouched, either the photosensitizer can be applied locally to the target area, or photosensitive targets can be locally excited with light. For instance, in the treatment of skin conditions, including acne, psoriasis, and also skin cancers, the photosensitizer can be applied topically and locally excited by a light source. In the local treatment of internal tissues and cancers, after photosensitizers have been administered intravenously, light can be delivered to the target area using endoscopes and fiber optic catheters....CLICK & SEE

CLICK & SEE THE ICTURES

Photosensitizers can also target many viral and microbial species, including HIV and MRSA. Using PDT, pathogens present in samples of blood and bone marrow can be decontaminated before the samples are used further for transfusions or transplants. PDT can also eradicate a wide variety of pathogens of the skin and of the oral cavities. Given the seriousness that drug resistant pathogens have now become, there is increasing research into PDT as a new antimicrobial therapy.

Photosensitizers:
In air and tissue, molecular oxygen occurs in a triplet state, whereas almost all other molecules are in a singlet state. Reactions between these are forbidden by quantum mechanics, thus oxygen is relatively non-reactive at physiological conditions. A photosensitizer is a chemical compound that can be promoted to an excited state upon absorption light and undergo intersystem crossing with oxygen to produce singlet oxygen. This species rapidly attacks any organic compounds it encounters, thus being highly cytotoxic. It is rapidly eliminated: in cells, the average lifetime is 3 µs.[5]

A wide array of photosensitizers for PDT exist. They can be divided into porphyrins, chlorophylls and dyes. Some examples include aminolevulinic acid (ALA), Silicon Phthalocyanine Pc 4, m-tetrahydroxyphenylchlorin (mTHPC), and mono-L-aspartyl chlorin e6 (NPe6).

Several photosensitizers are commercially available for clinical use, such as Allumera, Photofrin, Visudyne, Levulan, Foscan, Metvix, Hexvix, Cysview, and Laserphyrin, with others in development, e.g. Antrin, Photochlor, Photosens, Photrex, Lumacan, Cevira, Visonac, BF-200 ALA. Amphinex. Also Azadipyrromethenes.

Although these photosensitizers can be used for wildly different treatments, they all aim to achieve certain characteristics:

*High absorption at long wavelengths

*Tissue is much more transparent at longer wavelengths (~700–850 nm). Absorbing at longer wavelengths would allow the light to penetrate deeper,[8] and allow the treatment of larger tumors.

*High singlet oxygen quantum yield

*Low photobleaching to prevent degradation of the photosensitizer

*Natural fluorescence

*Many optical dosimetry techniques, such as fluorescence spectroscopy, depend on the drug being naturally fluorescent[10]

*High chemical stability

*Low dark toxicity

*The photosensitizer should not be harmful to the target tissue until the treatment beam is applied.

*Preferential uptake in target tissue

The major difference between different types of photosensitizers is in the parts of the cell that they target. Unlike in radiation therapy, where damage is done by targeting cell DNA, most photosensitizers target other cell structures. For example, mTHPC has been shown to localize in the nuclear envelope and do its damage there. In contrast, ALA has been found to localize in the mitochondria and Methylene Blue in the lysosomes.

To allow treatment of deeper tumours some researchers are using internal chemiluminescence to activate the photosensitiser.

PUVA therapy is using psoralen as photosensitiser and UVA ultraviolet as light source, but this form of therapy is usually classified as a separate form of therapy from photodynamic therapy.

Targeted PDT:
Some photosensitisers naturally accumulate in the endothelial cells of vascular tissue allowing ‘vascular targeted’ PDT, but there is also research to target the photosensitiser to the tumour (usually by linking it to antibodies or antibody fragments). It is currently only in pre-clinical studies.

Applications:
Compared to normal tissues, most types of cancers are especially active in both the uptake and accumulation of photosensitizers agents, which makes cancers especially vulnerable to PDT. Since photosensitizers can also have a high affinity for vascular endothelial cells.

Usage in acne:
PDT is currently in clinical trials to be used as a treatment for severe acne. Initial results have shown for it to be effective as a treatment only for severe acne, though some question whether it is better than existing acne treatments. The treatment causes severe redness and moderate to severe pain and burning sensation. A phase II trial, while it showed improvement occurred, failed to show improved response compared to the blue/violet light alone
Advantages:
There are several advantages of photodynamic therapy over other forms of facial rejuvenation. For example, PDT is less destructive (and therefore less painful) than many of the deeper peels and lasers. There is also minimal recovery time. It is also a proven technique for the treatment of precancerous lesions. Thus, depending on the technique used, there may be an additional benefit of preventing skin cancer.

Disadvantages:
The disadvantage of photodynamic therapy is that it is new. Long-term side effects are unknown, and the benefits are not as well studied. For example, PDT is not known how long the benefits last.

Although PDT is a promising new therapy, you need to discuss the risks, benefits, and alternatives with your physician to decide if PDT is right for you.
Modern development of PDT in Russia:
Of all the nations beginning to use PDT in the late 20th century, the Russians were the quickest to advance its use clinically and to make many developments. One early Russian development was a new photosensitizer called Photogem which, like HpD, was derived from haematoporphyrin in 1990 by Professor Andrey F. Mironov and coworkers in Moscow. Photogem was approved by the Ministry of Health of Russia and tested clinically from February 1992 to 1996. A pronounced therapeutic effect was observed in 91 percent of the 1500 patients that underwent PDT using Photogem, with 62 percent having a total tumor resolution. Of the remaining patients, a further 29 percent had a partial tumor resolution, where the tumour at least halved in size. In those patients that had been diagnosed early, 92 percent of the patients showed complete resolution of the tumour.

Around this time, Russian scientists also collaborated with NASA medical scientists who were looking at the use of LEDs as more suitable light sources, compared to lasers, for PDT applications.

Modern development of PDT in Asia:
PDT has also seen considerably development in Asia. Since 1990, the Chinese have been developing specialist clinical expertise with PDT using their own domestically produced photosensitizers, derived from Haematoporphyrin, and light sources. PDT in China is especially notable for the technical skill of specialists in effecting resolution of difficult to reach tumours
Resources:
http://en.wikipedia.org/wiki/Photodynamic_therapy
http://www.dermanetwork.org/information/pdt.asp