In vitro bioactivities and gastrointestinal simulation validate ethnomedicinal efficacy of five fermented kodo-based Himalayan traditional drinks and bioaccessibility of bioactive components

Tongba , chhyang , nigar and raksi are popular traditional drinks served in Nepal, northern and north eastern part of India and Tibetan plateau which are claimed as medicinal and considered as elements of high altitude ethnopharmacology. In this research, kodo (finger millet) based traditional beverages such as tongba , chhyang , nigar and raksi samples, collected from Singalila ridge of the Himalayas, were analysed through various qualitative and quantitative biochemical parameters. Total phenolic content (gallic acid equivalent) was estimated in a varied range from 936.26 ± 6.87 µg/mL ( nigar ) to 96.36 ± 1.22 µg/mL ( chimphing raksi ) while highest free fatty acid was measured in khokim raksi (2.11%). Antioxidant activity was evaluated using in vitro assays (DPPH assay, iodometric assay and in vitro anti-lipid peroxidation assay); antibacterial assay was conducted using well diffusion method. Tongba was found to be the most potential sample in antioxidant assays with a DPPH scavenging value of 85.31 ± 1.54% while nigar was the sample with most promising antibacterial activity. Furthermore, special emphasis was given on GC-MS based metabolite profiling and metabolomic elucidation. Responsible candidates detected by GC-MS analysis were discussed to correlate results of preliminary biochemical screenings and in vitro bioactivities. In vitro gastrointestinal digestion was carried out to figure out bioaccessibility of the bioactive groups of compounds in simulated human GI tract where DPPH assay, total phenol content and lipid composition (acid value) were considered as parameters. Most of the bioavailable bioactive antioxidants and phenolics were estimated to be decreased in the gastric phase reflecting the highest rate of digestion in the stomach while breakdown of lipid composition was dominated by the intestinal phase. Overall results suggest that antioxidative phenolics and fatty acids from these beverages possess bioactivities in their bioavailable form which may be associated to their ethnomedicinal properties. Graphical Abstract