Enhancing antioxidant and antimutagenic activity of the green seaweed Rhizoclonium riparium by bioassay-guided solvent partitioning

Rhizoclonium riparium is a filamentous green seaweed widely distributed along the coast of Sinaloa. Unfortunately, this seaweed remains unexploited despite having been described as an important source of bioactive molecules. Guided fractionation based on solvent partitioning is a common approach to screen for new natural bioactive compounds. By applying accurate design and interpretation among partition stages, this technique should permit an improvement in the bioactive response of extracts. Thus, the phytochemical composition and bioactivity of R. riparium fractions (FM methanol, FH hexane) obtained from acetone crude extracts (ACE) and sub-fractions from FM (FM1ethylacetate and FM2 water) by solvent partition were assessed. Chlorophyll and carotenoid content decreased during the partition process. The highest antioxidant activity of FM1, as assessed with the DPPH (2,2-diphenyl-1-picrylhydrazyl) test (501.39 Trolox equivalent antioxidant capacity or TEAC), was explained by the high total flavonoid (TFC) and phenol content (TPC). Moreover, a high flavonoid content led to the highest antioxidant activity being observed in FM, as assessed by ABTS^·+(2, 2′-azinobis [3-ethylbenzthiazoline]-6-sulphonic acid) reduction (449.59 TEAC). Apart from FM2, the remaining fractions exhibited a strong antimutagenic activity at 0.015 mg per plate (> 40%); FM1 showed the highest antimutagenic bioactivity in both tested bacterial strains (90.4% and 88% for strains TA98 and TA100) of Salmonella typhimurium. Results showed that bioassay-guided fractionation exerted a selective effect on the phytochemical profile that enhanced the antioxidant and antimutagenic activity of the extracts of R. riparium.