Chemical profile and in vitro bioactivity of tropical honey from Mauritius

To investigate into the antimicrobial and antioxidant potential of six varieties of honey from Mauritius. Six samples [commercial (processed, syrup-flavoured and ginger) and unifloral (eucalyptus, litchi and longan)] were assessed as traditionally used. The disc diffusion method was used against five microbial strains. Antioxidant capacity was determined using eight assays: trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power, iron chelating, hydroxyl radical (OH•), 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical scavenging assay, hypochlorous acid (HOCl), nitric oxide (NO•) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt radical scavenging assay. The total phenolic (TPC) and flavonoid content (TFC) were determined to delineate any correlation with any observed bioactivity. Longan honey showed the highest antimicrobial activity while processed and raw eucalyptus honeys showed moderate activity. TEAC ranged from (0.95±0.04) to (1.80±0.03) mmol trolox equivalents/100 g while ferric reducing antioxidant power varied between (160.77±1.02) to (170.50±1.84) mmol trolox equivalents/100 g. Strongest iron chelating activity was recorded for processed honey [IC50=(4.51±0.34) mg/mL] while eucalyptus and longan honeys had the highest OH• scavenging activity [IC50=(31.24±0.75) mg/mL and (31.30±0.85) mg/mL respectively]. Ginger honey had the lowest IC50 [(2.77±0.79) mg/mL] against NO• while longan honey was most active against HOCl• [IC50=(21.67±1.09) mg/mL] and processed honey showed the lowest IC50 against 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt radical [(90.44±2.48) mg/mL]. TPC ranged between (54.03±0.99) to (77.37±1.01) mg gallic acid equivalent/100 g and TFC between (4.55±0.06) to (11.80±0.20) μg rutin equivalent/100 g. Pearson correlation established strong correlations between antioxidant assays and TPC (TEAC: r=0.945 3; iron chelating: r=-0.696 4; OH•: r=-0.615 0; 2,2-diphenyl-1-picryl-hydrazyl-hydrate: r=-0.743 9) and TFC (HOCl•: r=-0.750 9; NO•: r=0.867 8). The current study has provided important baseline data on local honey which can be further exploited as a functional food.