Physicochemical characterization, polyphenols and flavonoids of different extracts from leaves of four varieties of tulsi (Ocimum sp.)

Leaves from four varieties of tulsi (Camphor, Krishna, Lavanga and Vishnu) were collected, dried and extracts were prepared using different solvents such as acetone, water, dichloromethane, ethanol, hexane and methanol. The total solids content in dried leaf powder was highest in Lavanga and Camphor, while Krishna showed the least. The study revealed that various secondary metabolites such as polyphenols and flavonoids were present in tulsi leaf extracts. The HPLC profiling showed the presence of rosmarinic acid in all the extracts irrespective of the solvent extraction. The other polyphenols present in the tulsi leaf extracts were p-coumaric acid, isothymucin, proto-catechic acid and caffeic acid. The GC-MS analysis of the extracts revealed methyl eugenol in Krishna variety with all the solvents, Bornanone in Lavanga and Camphor varieties in all the solvent extracts and caryophyllene in Vishnu variety. The LC-MS/MS profile of Krishna variety of tulsi showed mallic acid, citric acid, rosmarinic acid and asiatic acid as major compounds. The LC-MS/MS profile of Camphor variety of tulsi showed major peaks of compounds like mallic acid, citric acid, gallic acid, chlorogenic acid and asiatic acid. The LC-MS/MS profile of Lavanga variety of tulsi showed mallic acid, citric acid, gallic acid, asiatic acid and sumaresinolic acid as major compounds. Similarly in case of Vishnu variety, mallic acid, citric acid, gallic acid, apigenin, and sumaresinolic acid were present in majority. These phytochemicals from natural plant sources are known to possess many health benefits and considered as safe. Hence, these bioactive compounds may be explored for possible application as nutraceuticals.