Chapter 75 Centella asiatica (Gotu Kola)
Centella asiatica is an herbaceous perennial plant native to India, China, Indonesia, Australia, the South Pacific, Madagascar, and southern and middle Africa. This slender, creeping plant flourishes in and around water. Although it grows best in damp, swampy areas, centella is often observed growing along stone walls or other rocky, sunny areas at elevations of approximately 2000 feet in India and Sri Lanka.1
Depending on the environment, the form and shape of centella can change dramatically. In shallow water, centella forms floating leaves, whereas in dry locations, the leaves are small and thin, and numerous roots are formed.1
Typically, the constantly growing roots give rise to reddish stolons. The round-to-reniform, smooth-surfaced leaves, found on furrowed petioles, can reach a width of 1 inch and a length of 6 inches. The leaf margin may be smooth, crenate, or slightly lobed. Usually three to six red flowers arise in a sessile manner or on short pedicels in axillary umbels at the end of 0.08- to 0.3-inch long peduncles. The fruit, formed throughout the growing season, is approximately 0.2 inches long with seven to nine ribs and a curved, strongly thickened pericarp.1
Although the primary pharmacologically active constituents of C. asiatica are known to be triterpenoid compounds,2 its exact chemical profile is difficult to determine due to duplicate names and contradictory findings. In addition, centella samples from India, Sri Lanka, and Madagascar apparently do not contain the same constituents.3,4 In India, three (and possibly more) chemically different subspecies of C. asiatica have been found.5
The concentration of triterpenes in centella can vary between 1.1% and 8%, with most samples yielding a concentration between 2.2% and 3.4%.5 Figure 75-1 illustrates the major triterpenoid components of C. asiatica.
The Madagascar variety is most commonly used to produce standardized extracts. It yields triterpene concentrations of asiatic acid (29% to 30%), madecassic acid (29% to 30%), asiaticoside (40%), and madecassoside (1% to 2%).2
Centella also contains a green, volatile oil composed of an unidentified terpene acetate (which accounts for 36% of the total oil), camphor, cineole, and other essential oils. Centella oil also contains glycerides of fatty acids; various plant sterols such as campesterol, stigmasterol, and sitosterol; and various polyacetylene compounds.1,2
Centella has been used as a medicine in India since prehistoric times and is thought to be identical to the plant mandukaparni, listed in the Susruta Samhita (one of the valuable treatises in Ayurveda). Centella was also used extensively as a medicine, both internally and externally, by the people of Java and other islands of Indonesia. The medicinal use of centella in India and Indonesia centered around its ability to heal wounds and relieve leprosy, although it was also considered to be one of the “Rasayana”(rejuvenator) herbal medicines and was used to enhance memory and prolong life.1,2
In the nineteenth century, centella and its extracts were incorporated into the Indian pharmacopeia, in which, in addition to being recommended for wound healing, it was recommended for the treatment of skin conditions such as leprosy, lupus, varicose ulcers, eczema, and psoriasis. It was also used to treat diarrhea, fever, amenorrhea, and diseases of the female genitourinary tract.1
In China, the leaves are prescribed for turbid leukorrhea and toxic fevers, whereas the shoots are used for boils and fevers. The plant is also used in the treatment of fractures, contusions, strains, and snakebites.1 Centella was also used in China to delay senescence. One of the reported “miracle elixirs of life,” centella’s reputation as a promoter of longevity stems from the report of Chinese herbalist LiChing Yun, who reportedly lived 256 years. LiChing Yun’s longevity was supposedly a result of his regular use of an herbal mixture chiefly composed of centella.6,7
C. asiatica was first accepted as a drug in France in the 1880s. Since then, centella extracts have been used to treat many of the previously listed conditions, along with those described later in the section on “Clinical Applications”.
Centella, or gotu kola, has aroused much curiosity in American consumers. Many confuse gotu kola with kola nuts and assume gotu kola’s rejuvenating activity is nothing more than the stimulant effect of caffeine. However, gotu kola is not related to the kola nut (Cola nitida or Cola acuminata), nor does it contain any caffeine.
The majority of pharmacologic investigations on C. asiatica focused on the triterpene’s wound healing and venotonic activity.1,2 Although the exact mechanism of action has not yet been fully determined, a number of interesting observations have been made:
• In one of the early pharmacologic investigations of centella, Boiteau and Ratsimamanga8 demonstrated that asiaticoside substantially hastened the healing of experimentally induced wounds. These authors concluded that asiaticoside worked selectively in stimulating the rapid and healthy activity of the reticuloendothelial system.
• Additional studies on the mechanisms of action of centella’s enhancing wound healing showed that asiaticoside, given orally, by intramuscular injection, or by implantation to rats, mice, guinea pigs, and rabbits, produced a wide range of effects, as shown in Box 75-1.
• The efficacy of centella in stimulating collagen synthesis was demonstrated in human tissue cultures.13 Interestingly, this research also demonstrated an added benefit when vitamin C was added to the experimental cultures.
• The outcome of centella’s complex actions is a balanced multiphasic effect on cells and tissues participating in the process of healing, particularly in connective tissues. Enhanced development of the normal connective tissue matrix is perhaps the prime therapeutic action of C. asiatica.
More recent investigations focused on some of centella’s effects on the central nervous system, cognitive function, stress, and anxiety.2 The major effects are an enhancement of cholinergic mechanisms, as well as a significant antioxidant action via increasing glutathione levels.77,78 Presumably, these mechanisms are responsible for the improvements in mental function noted in both animal and clinical trials. Excellent results in improving cognitive function and memory were seen in animal models of Alzheimer’s disease.79
Obviously, from the brief description of centella’s pharmacologic activity given earlier, it is a valuable agent for the healing of wounds and treatment of venous insufficiency, and may also prove useful in improving mental function. Table 75-1 provides an abridged list of documented clinical applications of C. asiatica. The more popular uses of this valuable plant are discussed as follows in alphabetical order.
|Bladder ulcer||16, 17|
|Leprosy||11, 19, 35, 36|
|Peptic ulcer||39, 40|
|Surgical wound||8, 43, 49, 56–61|
|Venous disorder||63–75, 82–86|
|Wound healing||8, 43, 49, 56–61|
The standardized extract from C. asiatica has been used effectively in the treatment of patients with second- and third-degree burns caused by boiling water, electrical current, or gas explosion. Daily local application or intramuscular injections of the extract, or both, resulted in excellent results when treatment began immediately after the accident. The extract prevented or limited the shrinking and swelling of the skin caused by skin infection, and it inhibited scar formation, increased healing, and decreased fibrosis.18,19