Many drugs which are currently used in therapeutics have their origin in traditional medicine. The therapeutic efficacies of many indigenous plants for various diseases have been described by traditional herbal medicine practitioners. Natural products are a source of synthetic and traditional herbal medicine and have applications in primary health care. The presence of various active constituents in plants which positively impact on health, have encouraged scientists to investigate plants for various uses in medicine and have evinced interest in the management of wound healing particularly those of a chronic nature.

Normal wound healing response begins the moment the tissue is injured. The healing cascade begins immediately following injury when the platelets come into contact with exposed collagen. As platelet aggregation proceeds, clotting factors are released, resulting in the deposition of a fibrin clot at the site of injury. The fibrin clot serves as a provisional matrix and sets the stage for the subsequent events of healing. The inflammatory cells also arrive along with the platelets at the site of injury and they provide key signal chemicals, known as cytokines and growth factors (Lawrence and Diegelmann, 1994). The fibroblast is the connective tissue cell responsible for collagen deposition that is needed to repair the tissue injury. Collagen is the most abundant protein in the animal kingdom, accounting for 30% of the total protein in the human body. In normal tissues collagen provides strength, integrity and structure. When tissues are disrupted following injury, collagen is needed to repair the defect and restore anatomic structure and function.

The objectives of the study of wound healing are to investigate various influences on wound management and healing and to screen for potential drugs that promote healing. Several materials have so far been used and are reported to affect healing differently. Some rural communities still apply a paste made from the dried or wet leaves of several plant extracts on wounds. The use of fresh leaf extract of plants like cecropia peltata, Morinda citrifolia, Ixora coccinea, Vanda Roxburghii and Catharanthus roseus has been in practice in various countries with anecdotal reports of beneficial action. There is, however, a need to study and provide evidence for the efficacy of leaf extracts in the treatment of wounds. A search of literature gave us lots of information on the medicinal uses of plants available in Trinidad and Tobago. In our laboratory we have tested some of them like Morinda citrifolia (noni), Cecropia peltata (trumpet tree), Allamanda cathartica, Vanda Roxburghii and Catharanthus roseus (periwinkle, Old Maid) for their wound healing activity.

Morinda citrifolia L (Rubiaceae), also known as noni or Indian mulberry, is a small evergreen tree. It is one of the most important traditional Polynesian medicinal plants. Traditional Polynesian healers have apparently used the fruit for many purposes, including bowel disorders. The primary indigenous use of this plant, however, appears to be from the leaves, as a topical treatment for wound healing. Noni has been heavily promoted for a wide range of uses, including abrasions, arthritis, bladder infections, boils, bowel disorders, burns, cancer, colds, cold sores, congestion, constipation, diabetes, gastric ulcers, gingivitis, hypertension, improved digestion, immune weakness, indigestion, intestinal parasites, malaria, menstrual cramps, menstrual irregularities, mouth sores, ringworm, skin inflammation and wounds (Elkins, 1997). Several animal studies have evaluated the effects of extracts derived from noni. The results suggest noni may have anti-cancer, (Hirazumi et al., 1996; Hirazumi and Furusawa 1999) immune-enhancing, (Hiramatsu, 1993) and pain-relieving properties (Younos et al., 1990).

The corrosive and astringent latex of cecropias is used traditionally against warts, calluses, herpes, ulcers, dysentery, and venereal diseases (Caceres A et al, J Ethnopharmacology 1995). The leaves of Cecropia peltata are traditionally used for healing of wounds and lowering blood glucose. The tea made from the leaves is widely employed as a cure for asthma and is thought to be useful in treating a wide variety of other ailments and even snakebite.

Cecropia peltata Linn (cecropiaceae) also called trumpet-tree is a rapidly growing neo-tropical tree which is an important secondary species that is common in Puerto Rico. In South America it has been reported to be seen in Venezuela, Colombia, Brazil, and the Guianas.

We have used animal models to evaluate the wound healing activity of extracts of some common plants seen in Trinidad. Healthy inbred Sprague Dawley rats of both genders weighing between 200-220g were randomly distributed into three groups each of which were treated with a placebo (inert) material, a reference standard medication and the experimental extract. From acute toxicity studies (Jalalpure et al., 2003) an appropriate dose was calculated to evaluate wound-healing activity. The Animal Ethics Committee, Faculty of Medical Sciences, approved the study.

An excision wound model was used to evaluate the wound-healing activity of the plant extracts. The rats were inflicted with excision wounds (Morton and Malon, 1972). The animals were anaesthetized prior to and during creation of the wounds, with 1ml of intravenous ketamine hydrochloride (10mg/kg body weight) and shaved on both sides of the back with an electric clipper, and the area of the wound to be created was outlined on the back of the animals with methylene blue using a circular stainless steel stencil. A full thickness excision wound measuring 2.5cm length + 0.2cm depth (circular area = 4.9 square cm) was created along the markings using toothed forceps, a surgical blade and pointed scissors and the wounds were left open. Animals were treated with the controls and the plant extracts for ten days. We studied wound closure, epithelialisation time, collagen content and weight of granulation tissue. The wounds were measured on days 1, 5 and 11. The period of epithelialisation was determined from the number of days required for dead tissue remnants to fall off without any residual raw wound.

Granulation tissue which formed on the wounds was excised on the 11th post-operative day and weighed after oven drying. The hydroxyproline content of the dry tissues was estimated to determine the collagen and protein content (Neuman and Logan, 1950, Lowry et al., 1951). Additional sections were processed for histology workup.

We found that the plant extracts have properties that render them capable of promoting accelerated wound healing activity compared with placebo and standard treatment controls. We also noticed a significant increase in the collagen and protein content. The histological study of the healing tissue obtained from the animals treated with extract showed the early lay-down of collagen when compared with the control groups. Increased wound contraction and hydroxyproline content support further evaluation of these plants in the topical treatment and management of wounds. We in fact are planning to study other common plants in the healing of diabetic wounds with clinical investigators.

Our studies are early studies and are purely from animal experiments. These studies need to be explored in larger groups of animals to obtain consistent and reproducible results. Finally the application of the results to humans cannot simply be applied without detailed evaluation. The work was in joint collaboration by the Pre- and Para-Clinical Departments of the Faculty of Medical sciences and Department of Life Sciences, Faculty of Science and Agriculture. Our studies were funded by a research grant obtained from the Caribbean Health Research Council.