Metabolite profiling and in silico studies in critically endangered Himalayan medicinal plants Gentiana kurroo Royle and Swertia chirayita Roxb H Karst

Abstract

ABSTRACT newlineHimalayan medicinal herbs Gentiana kurroo Royle (GK) and Swertia chirayita (Roxb.) H. Karst. (SC) belonging to Gentianaceae family and found between 1500-5000 and 1200-2100 m a.s.l., respectively are enlisted as critically endangered by IUCN. These herbs are overexploited due to their metabolites like Gentiopicroside, Swertiamarin, etc. that bear phytochemical importance and possess hepatoprotective, anti-inflammatory, anti-diabetic, etc. activities. The study aimed to compare both plants for their biochemical, phytochemical and antioxidant potential; metabolite profiling using multianalytical techniques and in-silico metabolite interaction with six target receptors for therapeutic purposes. SC leaves (L) depicted higher chlorophyll, sugar and protein contents than those in GKL indicating relation of increasing protein content largely as Rubisco with higher photosynthetic activity (chlorophyll) and sugar as photosynthetic product. Positive correlation was observed amongst antioxidant enzyme activities (SOD, CAT, POD) and MDA contents in roots and leaves of both the plants. Phytochemical and antioxidant activities were evaluated in root (R) and leaf of both plants along with old (GKOF) and fresh (GKFF) flowers of GK. Ethyl acetate (EA) and methanol (ME) were better solvents for extracting phytochemical contents from roots and leaves of both the plants. Methanolic extracts depicted the highest antioxidant activities viz. total antioxidant in GKR and SCR (259.00±21.65 and 212.00±2.00 mg AAE g-1, respectively) and FRAP activity in GKR and SCL (49.06±1.28 and 8.03±0.02 mg AAE g-1, respectively). The IC50 values for DPPH radical scavenging (57.86±0.95 and#956;g mL-1) and metal chelating (41.84±0.17 and#956;g mL-1) activities in SCL aqueous (AQ) extract proved to be the best. The GKFF ME extract depicted higher phytochemical and antioxidant activities than GKOF ME. AAS analysis revealed similar macronutrient pattern (KgtSgtP) in GK and SC and GKL and SCL depicted similar micronutrient pattern (FegtBgtZngtMngtCu). Total 142 compounds were identified by GC-MS analysis in all six extracts. The GK flowers possessed highest compounds (32 in GKOF and 36 in GKFF), followed by leaves (15 in GKL and 29 in SCL) and roots (18 in GKR and 12 in SCR) of both the plants. Peaks obtained in FTIR spectra suggested presence of iridoid glycosides, xanthones, etc. in roots and leaves of both the plants. The 1H NMR spectroscopy of roots and leaves of both plants indicated presence of several bioactive constituents including Swertiamarin, Gentiopicroside, Mangiferin, Amaroswerin, Sweroside, Geniposide, and Genipin and presence of all except Amaroswerin was further confirmed by UHPLC-HRMS. The compounds identified by UHPLC-HRMS analysis through positive and negative (ESI+/ESI-) modes were Oxygeranial, Iridotrial, Loganic Acid, Secologanin, Sweroside, Swertiamarin and Gentiopicroside and thus, indicated distribution and accumulation of metabolites with plant part, growth and age. SCR reported higher content of Gentiopicroside and Swertiamarin (2.09 and 41.21 mg g-1 DW) than GKR. Metabolites Amaroswerin, Mangiferin along with Gentiopicroside and Swertiamarin depicted better docking scores against different receptors indicating their potential hepatoprotective, anti-diabetic and anti-inflammatory activities. Gentiopicroside and Swertiamarin were preferred metabolites as they followed Lipinsky Rule of Five and were also detected in 1H NMR and UHPLC-HRMS and further, quantified in HPLC. newline newline