Antioxidative potential of two chemically characterized Ocimum (Tulsi) species extracts

Abstract

Background: Ocimum sanctum and Ocimum kilimandscharicum are cultivated in Indian subcontinent both for the religious and medicinal properties. Traditionally, the leaves have been reported for their enormous therapeutic potentials but the roots which are otherwise considered as a waste part have not been explored for their pharmacological activity. Methods: Total phenolic content, free radical scavenging and ferric reducing antioxidant potential of various extracts from Ocimum sanctum and Ocimum kilimandscharicum were assessed and compared. In vitro antioxidant activity was estimated spectrophotometrically and the most potent ethyl acetate extract was chemically characterized by developing the chemical fingerprint and quantifying the probable constituents with the help of HPLC/LC-MS techniques. Results: The ethyl acetate extract of both the species exhibited significant free radical scavenging potential and also reduced the ferric ions. It was observed that ethyl acetate extract have superior ferric reducing potential than other tested extracts, which were evidenced by high ferrous sulphate equivalent value of 77.05 ± 1.54 and 80.98 ± 0.80 at 100 µg/ml for O. sanctum and O. kilimandscharium respectively. The ferric reducing capacity of ethyl acetate extract for both the species was also evidenced by an elevated optical density of 1.64 ± 0.12 and 2.14 ± 0.08. Ocimum sanctum exhibited better antioxidant capacity (11.31 ± 0.20 AScE) as compared to Ocimum kilimandscharium (9.08 ± 0.27 AScE). The total phenolic and flavonoid content were estimated by spectrophotometric method and tentatively characterized by HPLC/LC-MS profiling which revealed the presence of rosmarinic acid, caffeic acid along with its derivatives such as caffeoyl-dihydroxyphenyllactoyl-tartaric acid. Conclusion: The ethyl acetate extract of both the species being rich in phenolic and flavonoid contents exhibited potent antioxidant activity. The presence of flavonoid in ethyl acetate extracts further co-relates the antioxidative properties of roots extracts.  To the best of our knowledge and understanding this is the first report of comparative chemical profiling by RP-HPLC/LC-MS and antioxidant potential of roots of two Ocimum species. Peer Review Details Peer review method: Single-Blind (Peer-reviewers: 02) Peer-review policy Plagiarism software screening?: Yes Date of Original Submission: 27 July 2017 Date accepted: 23 August 2017 Peer reviewers approved by: Dr. Lili Hami Editor who approved publication: Dr. Phuc Van Pham