Accumulation of secondary metabolites in response to antioxidant activity of turmeric rhizomes co-inoculated with native arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria

•Increase in secondary metabolite contents of AMF inoculated turmeric rhizomes is reported.•Inoculated rhizomes showed strong antioxidant activities over control.•AMF ameliorate sustainable and quality production of turmeric rhizomes.

The present study was aimed at investigating the therapeutic potential of methanol crude extract of turmeric (Curcuma longa L.) rhizome co-inoculated with native arbuscular mycorrhizal fungi (Glomus, Gigaspora and Acaulospora sp.), phosphate solubilizer Bacillus megaterium and diazotrophic bacteria, Azospirillum amazonense and Azotobacter sp. To achieve the goals, parameters like free-radical (DPPH, ABTS) scavenging capacity, total phenolic contents, total flavonoids contents and percentage of curcumin content were examined. A significant increase of these secondary metabolites were observed in inoculated plants compared to non-inoculated controls revealing strong antioxidant activities of turmeric against DPPH and ABTS radicals in the range of 80–97%. The high amount of flavonoids (179.07–493.15 mg RE g−1), phenolic contents (83.07–151.54 mg GAE g−1) and percentage of curcumin (4.81–6.09%) present in all the methanolic extracts of dried rhizomes might be responsible for the observed antioxidant activity.