In Vitro Float Culture of Terminalia chebula (Retz.): Effect of Soybean Flour and Blue LEDs on Tannin Biosynthesis

Abstract

T. chebula (Retz.), one of the most widely used medicinal plants, produces diverse secondary metabolites. Cell culture of T. chebula was established by an inventive ‘Float culture’ wherein luffa sponge (dried mesocarp of Luffa aegyptiaca (Mill.) was used as a supporting matrix for the growing cell mass. The sterile seedlings were first germinated on an Aloe vera medium, consisting of Aloe barbadensis (Mill.) gel. The cotyledons of the germinated seedlings were used as explants for callus induction. Murashige and Skoog (1962) medium with 2,4-Dichlorophenoxyacetic acid (0.4mg/L) and Benzbrylaminopurine (0.6mg/L), and incubation in the dark at 30±2℃ were found to be optimal for callus induction. In order to optimise the medium and cultural conditions for the production of tannins, low-cost strategies such as soybean flour as an organic supplement, and a blue LEDs were employed. Comparative analyses revealed that the cultured cells could synthesise the complete array of metabolites that were detected in the fruit rind and leaf extracts. Quantitative analysis revealed that cells grown in MS (1962) medium with NAA (0.8mg/L), BAP (1.2mg/L), sugar 3% w/v and soy flour (200mg/L) with exposure to blue LED lights (144moles/m²/s) for 16h, produced highest level of gallic acid equivalents (0.4608mg/g dry weight). The fruit rind extract and callus extract were tested in the laboratory for their antimicrobial activity against potent enteric pathogens, viz. E. coli, Vibrio cholerae, Salmonella enterica, Shigella boydii and Staphylococcus aureus. The fruit rind extract of the plant exhibited high antimicrobial activity against all the tested bacterial species. The callus extract also exhibited zone of inhibition 21 cm for E. coli, 17 mm for Salmonella enterica, 17 mm for Shigella boydii, and 14 mm for S. aureus. The study points to the utility of ‘Float culture’ for the production of valuable pharmaceuticals.