Fermentation, a feasible strategy for enhancing bioactivity of herbal medicines

• Fermentation is beneficial for the therapeutic applications of many herbal medicines.
• Fermented herbal medicines are known to be enriched with a variety of anti-oxidants.
• In many cases, fermentation improves the therapeutic efficacies of herbal drugs.
• The toxicities of fermented herbal medicines must be evaluated before marketing.
• Future studies are required to judge the potential of this area in drug development.

Herbal drugs, which possess immunomodulatory, anti-inflammatory, anti-diabetic, anti-infective, and anti-allergic activities, encompass various therapeutic areas, and have been used as traditional medicines for thousands of years. Fermentation is an indispensable traditional technology for the improving the efficacy or reducing adverse effects of herbal medicines. The fermentation process has been shown to improve biological properties of plants, vegetables, and herbs. More specifically, fermentation causes decomposition and/or biotransformation of complex substrates into compatible components, thereby modulating product properties or changing the quantity of certain bioactive compounds. Accumulating evidence indicates the valuable contribution of probiotics and their fermented food products to health. In recent years, considerable attention has been paid to fermentation technology across the globe for improving herbal drugs through production and enrichment of additional bioactive metabolites of medicinal importance including isoflavones, saponins, phytosterols, and phenols. For example, the phenolic contents of the herbal preparation can be increased as a consequence of fermentation and a positive correlation between polyphenols and the anti-oxidant activities of herbs has been well demonstrated. This is in agreement with evidence showing fermentation-mediated enhancement of the pharmacological properties and therapeutic efficacies of herbal formulations against a number of diseases including obesity and inflammation. The subject of fermentation of herbal preparations has been maturing and gaining considerable attention of scientific and technical communities worldwide. In the current review we have addressed these issues in detail with emphasis on understanding the contribution of fermentation-derived bioactive substances to therapies against a number of diseases.