Advances and emerging research trends for modulation of centelloside biosynthesis in Centella asiatica (L.) Urban- A review

This review highlights the current status of various biotechnological efforts made in Centella asiatica (L.) Urban, extensively used medicinal herb in the traditional as well as modern systems of medicines. Published literature on the development and testing of various in vitro cell/tissue/organ culture-based protocols for biomass and metabolites yield enhancement has been compiled and presented here with an intention to identify research gaps that need more closer prospection for their industrial translation and up-scaling. Emphasis has also been laid in listing some of the pathway flux limiting enzymes/genes that demand more concerted efforts for their translational up-regulation in this medicinal herb. Centella asiatica is commonly known as Gotu Kola, Asiatic Pennywort or Brahmi in the herbal trade and is an important constituents of > 100 health care formulations sold in the market. The plant and its chemical constituents are frequently used for the treatment of several nootropic disorders, memory loss, platelets aggregation, insomnia, psoriasis, burn wounds, hypertonic scars, and skin cell reconstruction and curing. Centella derives most of its pharmacological activities from four major bioactive triterpene glycosides namely, asiaticoside, madecassoside, asiatic acid, and madecassic acid (collectively called as centellosides). Plants with at least 2% content of asiaticoside and madecassoside are generally preferred by the herbal industries. In India, 500-1000 MT of Centella herb priced at 0.4-0.5 US dollars/kg is traded annually. Like several other medicinal plants, more than 90% of the supply of C. asiatica herb to the industry is met through collection from the wild strands, which is neither sustainable nor quality-driven. The plant is already included in the International Union for Conservation of Nature and National Resources Red Data book of threatened species. A scan of published literature on C. asiatica clearly indicates that while advances made in the fields of chemistry and bioactivity assessment of centellosides have been regularly reviewed, a compilation of data on tissue culture, pathway modulation and metabolic engineering efforts made in this herb is lacking. The present review is an attempt to fill this gap.