Characterization of polyphenols by RP-HPLC in Basilicum polystachyon (L.) Moench with their antioxidant and antimicrobial properties

Abstract

• Ultrasonic assisted leaf extract of Basilicum polystachyon revealed the phenolic compounds present in the free, esterified and glycosylated forms. • First comparative RP-HPLC analysis of different phenolic forms in vivo and in vitro B. polystachyon leaf. • Gallic acid, trans -cinnamic acid, ellagic acid, quercetin and vanillic acid in B. polystachyon for the first time along with caffeic acid, p- coumaric acid and rosmarinic acid were identified. • B. polystachyon could serve as a souce of antioxidants. • Phenolic compounds of in vivo plants exhibited the higher antimicrobial activities against B. subtilis, S. aureus, M. smegmatis, E. coli and C. albicans. Basilicum polystachyon (L.) Moench is a member of Lamiaceae family and important ethnomedicinal that is widely used in the treatment of several ailments and is reputed to possess an inhibitor of the dengue virus. In vitro propagation is an efficient strategy for large-scale production of plantlets. Such process is a good alternative method for the production of valuable secondary metabolites. Hence, the present study assesses the contents of phenolic compounds, radical scavenging activity and antimicrobial efficacy of in vivo grown compared with the in vitro grown B. polystachyon plants. Thus, the antioxidant capacity of leaf extracts was determined by scavengers like ABTS .+ , DPPH . , hydrogen peroxide, hydroxyl radical, nitric oxide along with lipid peroxidation inhibition, FRAP, reducing power and DNA damage protection assay. The antimicrobial activity was evaluated through disk diffusion assay and minimum inhibitory concentration assay. RP-HPLC was used to identify and quantify the phenolic compounds in the following forms: free, esterified and glycosylated. The leaf extract of in vivo plants exhibited stronger antioxidant activities. The FRAP assay revealed a maximum reducing power with leaf extract of in vivo grown plants (43.73±0.52 µM Fe(II) equivalent). Total phenolic content of in vivo plants presented a strong positive correlation to IC 50 values of ABTS, DPPH, and HPSA, whereas total flavonoid content of in vitro grown plant was strongly correlated to IC 50 values of DPPH and HPSA. In vivo plants showed the highest inhibition zone against Bacillus subtilis, Escherichia coli , and Staphylococcus aureus. RP-HPLC analysis showed the phenolic compounds present in all tested forms of B. polystachyon leaf. For the first time, gallic acid, trans -cinnamic acid, ellagic acid, quercetin and vanillic acid were identified in this extract. Also, caffeic acid, p -coumaric acid and rosmarinic acid were quantified. These findings strongly suggest that B. polystachyon may be exploited as a promising natural source of antioxidants along with efficient antimicrobial agents.