Pennywort Centella asiatica Origin
Centella asiatica (CA) or Pennywort is a clonal, perennial herbaceous creeper belonging to the family Umbellifere (Apiceae). This plant is found in most tropical and subtropical countries. Growing in swampy areas, including parts of India, Pakistan, Sri Lanka, Madagascar, and South Africa, Indonesia, South pacific and Eastern Europe. About 20 species related to CA grow in most parts of the tropic or wet pantropical areas such as rice paddies, and also in rocky, higher elevations. It is a tasteless, odourless plant that thrives in and around water.
Pennywort has small fan-shaped green leaves with white or light purple-to-pink or white flowers and it bears small oval fruit . The whole plant is used for medicinal purposes. It is widely used as a blood purifier as well as for treating high blood pressure, for memory enhancement and promoting longevity. In Ayurveda, CA is one of the main herbs for revitalizing the nerves and brain cells. Eastern healers relied on CA to treat emotional disorders, such as depression, that were thought to be rooted in physical problems. In the Western medicine, during the middle of the twentieth century, CA and its alcohol extracts reported to have shown positive results in the treatment of leprosy.
The primary active constituents of CA are saponins (also called triterpenoids), which include asiaticosides, in which a trisaccharide moiety is linked to the aglycone asiatic acid, madecassoside and madasiatic acid. These triterpene saponins and their sapogenins are mainly responsible for the wound healing and vascular effects by inhibiting the production of collagen at the wound site. Other components isolated from CA, such as brahmoside and brahminoside, may be responsible for CNS and uterorelaxant actions, but are yet to be confirmed by clinical studies. Centelloside and its derivatives are found to be effective in the treatment of venous hypertension.
Efficacy of Pennywort
CA might assist in the maintenance of connective tissue. In the treatment of scleroderma, it might also assist in stabilizing connective tissue growth, reducing its formation as it reportedly stimulated the formation of hyaluronidase and chondroitin sulfate, as well as exerted a balancing effect on the connective tissue. CA was reported to act on the connective tissues of the vascular wall, being effective in hypertensive microangiopathy and venous insufficiency and decreasing capillary filtration rate by improving microcirculatory parameters.
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Sedative and anxiolytic properties
CA was described to possess CNS effects in Indian literature such as stimulatory-nervine tonic, rejuvenant, sedative, tranquilizer and intelligence promoting property. Pennywort has been traditionally used as a sedative agent in many Eastern cultures; the effect was postulated mainly due to the brahmoside and brahminoside constituents, while the anxiolytic activity is considered to be, in part due to binding to cholecystokinin receptors.
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The antidepressant effects of total triterpenes from CA on the immobility time in forced swimming mice and concentration of amino acid in mice brain tissue was observed. In the study, imipramine and total triterpenes from CA reduced the immobility time and ameliorated the imbalance of amino acid levels confirming the antidepressant activity of CA.
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Asian CA traditionally used as anxiolytic and anticonvulsant. The isolated steroids from the plant have been used to treat leprosy. A research suggested the potential of aqueous Pennywort extract as adjuvant to antiepileptic drugs with an added advantage of preventing cognitive impairment. Various experimental models found Pennywort show protective action against increase in intracranial electric stimulation (ICES) and chemo-convulsions. It also showed a reduction in formation of lipid peroxidation products, reduction in spontaneous motor activity, potentiation in diazepam withdrawal-induced hyperactivity, hypothermia, and potentiation of pentobarbitone sleeping time.
Cognitive and antioxidant
CA is known to re-vitalize the brain and nervous system, increase attention span and concentration and combat aging. A study demonstrated cognitive-enhancing and anti-oxidant properties of CA in normal rats. A research suggested the potential efficacy of CA in preventing the cognitive deficits, as well as the oxidative stress. In one study, derivatives of asiatic acid derivatives were shown to exert significant neuroprotective effects on cultured cortical cells by their potentiation of the cellular oxidative defence mechanism. Therefore, these agents were proved to be efficacious in protecting neurons from the oxidative damage caused by exposure to excess glutamate.
A laboratory study was reported in which aqueous extract of CA was found to be effective in inhibiting gastric lesions induced by ethanol administration. The authors concluded that the CA extract presumably strengthened the gastric mucosal barrier and reduced the damaging effects of free radicals. Both the drugs and the herb extract showed a dose-dependent reduction of gastric ulceration, which, except for the antiulcer effect of famotidine, could be reversed with bicucullin methiodide. One study showed that CA and its constituents, asiaticosides have an anti-inflammatory property that was brought about by inhibition of nitric oxide (NO) and thus facilitating ulcer healing. Some other researchers also showed the efficacy of CA through preclinical and clinical studies for healing gastric ulcers. CA has also been investigated to demonstrate its role in periodontal therapy.
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Antinociceptive and antiinflammatory
The aqueous CAE revealed significant antinociceptive activity with both the models similar to aspirin but less potent than morphine and significant antiinflammatory activity comparable to mefenamic acid. These results suggested that the aqueous CA extracts possesses antinociceptive and antiinflammatory activities which justified the traditional use of this plant in the treatment of inflammatory conditions or rheumatism.
Previous studies have suggested that CA could be useful in preventing radiation-induced behavioural changes during clinical radiotherapy. The plant extracts were also tested for its radioprotective properties at a sublethal dose (8 Gy) of Co 60 gamma radiation. A 100 mg/kg dose increased the survival time of the mice significantly. Body weight loss of the animals in the drug treated group was significantly less in comparison with the animals that were given radiation only.
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The CA extracts (CAE) have been used traditionally for wound healing and the research has been increasingly supportive for these claims. A preclinical study reported that various formulations (ointment, cream, and gel) of an aqueous CAE applied to open wounds in rats (3 times daily for 24 days) resulted in increased cellular proliferation and collagen synthesis at the wound site, as shown by an increase in collagen content and tensile strength. The authors found that the CAE-treated wounds epithelialized faster and the rate of wound contraction was higher when compared to the untreated control wounds. In one laboratory animal study, the authors concluded that asiaticosides may have enhanced the induction of antioxidants at an initial stage of wound healing, but continued application of the preparation seemed not to increase the antioxidant levels in wound healing.
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Source: Pharmacological Review on Centella asiatica: A Potential Herbal Cure-all.”. Indian J Pharm Sci: 546–56. September 2010.