Table 3 Non-experimental validation of plants used for skin problems in Trinidad and Tobago

Achyranthes aspera

Achyranthes bidentata is a commonly used Chinese medicinal plant and is used in Nepal and in Mauritius and Rodrigues for skin diseases. Achyranthes bidentata polysaccharide can inhibit non-enzyme glycation in D-galactose induced mouse aging model in vivo. Achyranthes aspera leaf extract and the non-alkaloid fraction containing mainly non-polar compounds have chemo-preventive activity.

8–10

Azadirachta indica

A paste made of Azadirachta indica and Curcuma longa used to treat 814 people with scabies cured 97% of them within three to five days of treatment. Azadirachta indica (leaves, bark, fruit, flowers, oil, and gum) have the following properties: antimicrobial effects, in vitro antiviral activity, and antibacterial activity. Some active principles of Azadirachta indica are azadirachtin, salannin nimbin, and 6-desacetylnimbin. Clinical symptoms associated with toxocariasis in 1009 Trinidadian schoolchildren (aged 5–12 years) included eczema.

11–14

Bidens pilosa

Bidens pilosa is a commonly used traditional Chinese medicine.Bidens pilosa contains ethyl caffeate, a natural phenolic compound. Extracts of dried aerial parts of Bidens pilosa showed some antimicrobial activity as do components of the extract such as phenylheptatriyne, linolic acid and linolenic acid. The triterpenes as well as several flavonoids (aurones, chalcones) are antiinflammatory agents. The chloroform fractions from the roots of Bidens aurea are anti- parasitical in vitro. The constituents of Bidens pilosa explain the use of this plant in traditional medicine in the treatment of wounds, against inflammations and against bacterial infections of the gastrointestinal tract.

15–17

Cassia alata

"Jue ming zi" (Cassia tora L. and Cassia occidentalis L.) has traditionally been used to improve visual acuity and to remove "heat" from the liver in Chinese medicine. Modern physicians use "Jue ming zi" to treat hypercholesterolemia and hypertension. "Jue ming zi" contains chrysophenol, emodin, and rhein. Roasted "Jue ming zi" is given as a health drink tea. The antioxidant activity of the methanolic extracts of "Jue ming zi" (Cassia tora L. and Cassia occidentalis L.) was established. Cassia alata is used for skin problems in the Caribbean, India, in traditional East Asian medicine and in the Ivory Coast (West Africa) to treat bacterial infections caused by Escherichia coli, and fungal infections caused by Candida albicans and dermatophytes. Cassia alata L. possesses anti-inflammatory, analgesic, laxative and antiplatelet aggregating activity and it contains kaempferol-3-O-gentiobioside. Cassia alata has antifungal activity that may be attributed to chrysophanol. When Cassia alata extracts were evaluated relative to a standard antibacterial agent chloramphenicol and antifungal agent amphotericin B the extracts had therapeutic potential for the treatment of opportunistic infections of AIDS patients. A 10-year human study indicated that a Cassia alata leaf extract can be reliably used as a folk medicine to treat Pityriasis versicolor. The leaf extract contains anthraquinones, flavonoids, quinones and sterols and had no side-effects.

18–21

Chamaesyce hirta

Chamaesyce hirta is used in West Bengal for ringworm. Antibacterial effects of Chamaesyce hirta leaves were found by several investigators. An aqueous extract of Chamaesyce hirta strongly reduced the release of prostaglandins I2, E2, and D2. Additionally Chamaesyce hirta extracts exerted an inhibitory effect on platelet aggregation and depressed the formation of carrageenin-induced rat paw oedema.

22

Croton gossypifolius

Croton cascarilloides wood has been used historically to blacken teeth in Asia. Croton cascarilloides wood soot has limited antimicrobial activity against Mutans streptococci. Croton species are used in Thailand to treat dysmenorrhea, gastric ulcers, gastric cancers, and dysentery. Croton kongensis Gagnep., is known in Thailand as "Plao Ngeon" or "Plao Noi". A crude CH2Cl2 extract of Croton kongensis showed antimalarial and antimycobacterial activities. Croton sylvaticus showed 5-lipoxygenase inhibitory activity with IC(50) values <61 ppm. A review of papers published in 2003, found that in vitro and in vivo studies supported the use of Croton lechleri Mull. Arg. for wounds, tumors, herpes infection, the itching, pain and swelling of insect bites and other conditions.

23–26

Eclipta prostrata

Eclipta prostrata is commonly used as self medication by AIDS patients in southern Thailand and showed potential as a therapeutic agent against Giardia intestinalis infections. The hydroalcoholic extract of Eclipta prostrata plant showed antinociceptive, immunomodulatory and antiinflammatory effects.

27

Origanum vulgare

Origanum volatile oil has potential efficacy against the infection of dysentery bacteria (Shigella sonne (Sh. sonnei) and Shigella flexneri). The carvacrol constituent has the most effective antimicrobial activity in Origanum vulgare. Diarrheic children in Trinidad were positive for Shigella (33 or 14.0%), 4 for Salmonella, and 1 for Enteropathogenic E. coli. Two fecal samples were positive for Campylobacter jejuni, and 1 was positive for hookworm ova.

28–30

Sida acuta

Sida acuta contains ecdysterone, ephedrine, hentriacontane, hypolaetin-8-glucoside, beta sitosterol, stigmasterol and campesterol. These chemicals may be responsible for the plant's reported narcotic analgesic, anti-inflammatory and analgesic activity.

31

Solanum americanum

Solanum americanum extracts were active against Microsporum gypseum and Cryptococcus neoformans and showed intra-peritoneal subacute toxicity in mice. Alpha-solamargine isolated from the fresh fruits of Solanum americanum is a glycoalkaloid with biological activity against Herpes simplex I, Herpes zoster and genital Herpes and Trypanosoma cruzi. Solanum melongena contains an anthocyanin, delphinidin, which inhibits the collagenolytic ability of matrix metalloproteinases.

32, 33