Table 2.

Neurotherapeutic effects of Withania somnifera, Bacopa monnieri, Gingko biloba, Centella asiatica, Crocus sativus, Curcuma longa, and Fuzhisan in randomized, placebo controlled human trials. In these trials, no severe adverse effects were noted for any of the administered extracts or natural compounds.

Herb	Conducted By	Study Design	Sample Size	Dosage Regimen	Metrics Tested	Findings
Withania somnifera	Pingali et al. [53]	Randomized, placebo controlled, double-blind study	20	250 mg twice daily for 14 days	Reaction time, choice discrimination, digit symbol substitution, digit vigilance, card sorting tests, finger-tapping test	Significant improvement in reaction time, choice discrimination, digit vigilance, card sorting tests, and digit symbol substation No effect in finger-tapping test
Bacopa monnieri	Raghav et al. [58]	Randomized, placebo controlled, double-blind study	40	125 mg twice daily for 12 weeks, followed by 4 weeks of placebo (16-week total duration)	Mental control, logical memory, digit forward, digit backward, visual reproduction and paired-associate learning	Significant improvement in mental control, logical memory, and paired-associate learning
Gingko biloba	Le Bars et al. [126]	Randomized, placebo controlled, double-blind study	309	120 mg once daily for 52 weeks	ADAS-Cog	Modest improvement in cognitive performance measured by ADAS-Cog and noted by caregivers
Centella asiatica	Wattanathorn et al. [136]	Randomized, placebo controlled, double-blind study	28	250, 500, and 750 mg once daily for 8 weeks	Bond–Lader mood scale, alert factor, content factor, calm factor, word recognition, image recognition	Increased accuracy in word recognition, image recognition, alertness, and calmness, with high dosage showing greater effects. No significant difference in content factor between treatment and placebo groups.
Crocus sativus	Akhondzadeh et al. [69]	Randomized, placebo controlled, double-blind study	22	15 mg twice daily for 22 weeks	ADAS-Cog	Effectively similar to 10 mg daily of donepezil in the ADAS-Cog scale
Curcuma longa	Baum et al. [173]	Randomized, placebo controlled, double-blind study	34	1000 to 4000 mg once daily for 26 weeks	ADAS-Cog	No cognitive decline in enrolled subjects during study duration
Fuzhisan (Anemone altaica, Glycyrrhiza uralensis, Scutellaria baicalensis, Panax ginseng)	Bi et al. [76]	Randomized, placebo controlled, double-blind study	22	10 mg once daily for 12 weeks	ADAS-Cog, neuropsychiatric index	Significantly improved ADAS-Cog and neuropsychiatric index scores compared to placebo