Centella asiatica (Mandookaparni or Gotu Kola)
Centella asiatica is reputed for its beneficial effects in various neurological disorders. Gotu Kola has been used for centuries in Ayurvedic and traditional Chinese medicine to alleviate symptoms of depression and anxiety. Recent studies in the rat have shown that long-term pretreatment with Gotu Kola decreases locomotor activity, enhance elevated-plus maze performance and attenuate acoustic startle response. In a double-blind, placebo-controlled study, the anxiolytic activity of Centella asiatica in healthy subjects was undertaken and compared to placebo, Gotu Kola significantly reduced peak acoustic startle response amplitude 30 and 60 minutes after treatment. In another clinical study, 70% hydroethanolic extract of Centella asiatica was given to 33 participants for two months and Hamilton’s Brief Psychiatric Rating Scale (BPRS) was used to screen the subjects. The results show that, Mandookaparni significantly attenuated anxiety related disorders. These preliminary findings suggest that Centella asiatica has anxiolytic activity in humans and it remains to be seen whether this herb has therapeutic efficacy in the treatment of anxiety syndromes in large population.
Bacopa monnieri (Brahmi)
In Indian traditional medicine, several herbs have been used as nerve tonics. The most popular of these herbs is brahmi, a well known memory booster. This herb is used by Ayurvedic medical practitioners for almost 3000 years. The traditional use of brahmi as an anti-anxiety remedy in Ayurvedic medicine is supported by both animal and clinical studies. Brahmi is used in Indian tradition medicine in treatment of number of brain disorders namely anxiety and poor memory. Pharmacologically, Bacopa monnieri comprises of five major saponins: bacoside A3, bacopaside II, bacopasaponin C isomer, bacopasaponin C and bacopaside I. Bacopa monniera extract or its constituent bacosides showed anxiolytic activity in animals and Singh et al. suggest an involvement of the GABA-ergic activity in brahmi’s action on central nervous system. Brahmi not only enhances memory, it also shows an anti-stress effect. Pretreatment with Bacosides resulted in decrease Hsp expression in the hippocampus; it restored P450 enzyme activity and increased superoxide dismutase activity in the stressed rats. Brahmi modulates the activities of Hsp70, P450 and SOD and thereby protects the brain from deleterious effect of stress. In another study, pretreatment with brahmi restored both acute and chronic immobilization stress-induced changes in ulcer index, adrenal gland weight, creatine kinase, and aspartate aminotransferase. Treatment with Bacopa monnieri extract 40 mg/kg/day effectively reversed behavioral deficits of PCAPP mice in open field tests compared with non-transgenic controls.
Previous clinical study demonstrated that administration of brahmi syrup to 35 patients diagnosed with anxiety neurosis resulted in significant decrease in anxiety symptoms and level of anxiety. In a recent randomized, double-blind, placebo controlled clinical trial, effect of standardized Bacopa monniera extract in healthy elderly patients on anxiety, depression and recall memory was evaluated. Bacopa participants had enhanced delayed word recall memory scores in Rey Auditory Verbal Learning Test (AVLT) compared to placebo. Affective measures like depression scores, anxiety scores, and heart rate decreased in due course for the Bacopa group but increased for the placebo group. In a study by Stough et al., the chronic effects of brahmi extract were examined on memory function in forty six healthy human subjects aged between 18 to 60 years. The study was a double-blind placebo-controlled independent group design in which subjects were randomly allocated to one of the two treatment conditions, i.e., brahmi extract (300 mg) or placebo. Neuropsychological tests were conducted pre-baseline and at 5 and 12 weeks post-drug administration. Brahmi extract significantly improved speed of visual information processing measured by the Inspection Time, learning rate and memory consolidation measured by Auditory Verbal Learning Test, and state anxiety examined using Strait-Trait Anxiety Inventory. The results of the clinical trial suggested that brahmi extract improved higher order cognitive processes that are critically dependent on the input of information from our environment such as learning and memory. Another study to measure the effect of brahmi extract on human memory was conducted by Roodenrys et al.. Seventy six adults aged between 40 and 65 years volunteered for the double-blind randomized, placebo control study in which various memory functions were tested and levels of anxiety measured in three testing sessions: one prior to the trial, one after three months on the trial, and one six weeks after the completion of the trial. The results showed a significant effect of brahmi on the test for the retention of new information. In the follow-up tests it was found that the rate of learning was unaffected, suggesting that brahmi decreases the rate of forgetting of newly acquired information.
Withania somnifera (ashwagandha)
This has been an important herb in use within Ayurvedic and indigenous medical systems for over 3000 years. Both preclinical and clinical studies demonstrate the use of ashwagandha for anxiety, inflammation, Parkinson’s disease, cognitive and neurological disorders. It is also used therapeutically as an adaptogen in nervous exhaustion, insomnia, debility due to stress. Preclinically, the extract of Withania somnifera (WS) root exhibited anxiolytic activity in the elevated plusmaze, social interaction and feeding latency in an unfamiliar environment. Chronic stress-induced hyperglycemia, cognitive deficits, immunosupression and depression was attenuated by ashwagandha. The results indicate that ashwagandha has significant antistress adaptogenic activity, confirming the clinical use of the plant in Ayurveda. A recent study has demonstrated the anxiolytic potential of a compound natural health product which had Withania as the main herb in an open label human trial. Also, studies have demonstrated that WS possesses GABA-mimetic properties. Since GAB A agonism has been linked to anxiolysis, the extracts of WS may have beneficial effect in anxiety and related disorders. A double blind placebo control study in patients with ICD-10 anxiety disorders, 6 weeks treatment with ethanolic extract of W. somnifera showed anxiolytic activity over placebo. The extract was well tolerated and did not cause more adverse effects than placebo. So, it was concluded that the ethanolic extract of WS has useful anxiolytic potential.