Metabolome analysis of Dactylorhiza hatagirea (D. Don) Soo reveals a significant antioxidant and nutritional potential of its tubers

Abstract

Dactylorhiza hatagirea (D.Don) Soo (Vern. Salam Panja) is a highly valued terrestrial dietary orchid from Himalaya, whose tubers are traded for possessing medicinal uses to human health benefits. The current research was focused on chemical exploration, along with evaluation of the nutritional and antioxidant potential, of its tuber extracts, which were procured from traders as well as from its natural habitats. Total phenolics, flavonoids, sugars, amino acids, macro- and micro- elements were estimated in the tuber extracts. It was found that phenolics and flavonoids (73.61 ± 0.92 and 48.59 ± 0.71 mg/g) were higher in methanolic extracts of marketed sample (DH 2 ) than DH 1 , the methanolic extract of sample collected from natural habitat. The free amino acids and sugars were also found promisingly. The extracts showed antioxidant potentials with IC 50 ranges from 1.58 to 4.41 and from 0.19 to 0.48, mg/mL in DPPH and ABTS assays, respectively. Further, UPLC-DAD analysis revealed the presence of vanillic acid in all samples (ranging from 0.21 to 0.58 mg/g). Further, dactylorhin A (0.12–0.81 mg/g) and B (0.62–0.88 mg/g) were also determined in all the samples except water extract (DH 5 ). Further, UHPLC-QTOF-IMS analysis enabled the identification of 152 diversified metabolites such as sugars, terpenoids, steroids, amino acids, polyphenols, nucleosides, saponins, organic and fatty acids. The heavy metals (Cd, Hg, Pd, As) were absent while the micro- (Mn, Na, Zn, Cu) and macro- (Ca, Fe, Mg, K) elements were present in tubers. Furthermore, the variability in diversity of targeted metabolites was visualized using multivariate analysis and accounting 77.169 and 17.62% variance in PC1 and PC2 components, respectively. The current finding unleashed the chemical information including tentative biosynthesis of metabolites, nutraceutical and medicinal values of dietary orchid. Thus, this research will contribute to future agricultural and biotechnological interventions for a higher quality produce, thereby reducing ‘over-exploitation’ pressures on natural populations and also contributing to sustainable generation of this important bioresource. . • Total phenolic and flavonoid contents were higher in methanolic extracts of D. hatagirea tubers. • Vanillic acid, dactylorhin A and dactylorhin Bwere quantified using UPLC-PDA. • The environmental toxins (Cd, Hg, Pd, As) were absent in all the extracts. • 152 metabolites were identified using UHPLC-QTOF-IMS and METLIN database in D. hatagirea . • DPPH and ABTS assays revealed antioxidant activity.