Comparative evaluation of extraction solvents/techniques for antioxidant potential and phytochemical composition from roots of Nepeta leucophylla and quantification of polyphenolic constituents by RP-HPLC-DAD

Abstract

In the present study, the extraction techniques like maceration, ultrasound and soxhlet extraction were employed to obtain different extracts from the powdered roots of Nepeta leucophylla using the solvents of different polarity and the percentage yield of the different extracts was compared. These extracts were screened for their total polyphenolic content (TPC), total flavonoids content (TFC) and for their antioxidant potential using different assays like 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), nitric oxide scavenging, ferric reducing antioxidant power (FRAP) and total antioxidant capacity (TAC). The results of percentage yield of different extracts ranged from 0.9 to 8.07 %. The methanol extract obtained by Soxhlet method showed a higher value of TPC [94.02 mg GAE/g of dry plant extract (DPE)], FRAP (130.75 mg Fe(II) E/g of DPE), percentage inhibition of DPPH (91.4 %) and NO scavenging (51.6 %), whereas the same extract obtained by ultrasound assisted extraction method showed higher values of TFC (228.75 mg RE/g of DPE) and TAC (40.8 mg AAE/g of DPE) as compared to all other extracts. Reverse phase high-performance liquid chromatography-photodiode array detector analysis showed the presence of myricetin, caffeic acid, catechin hydrate and vanillic acid as key polyphenolic in the different methanol extracts, whereas gas chromatography mass spectrometry analysis showed the presence of long chain hydrocarbons, steroids, fatty acids and benzoid classes of natural products.