Comparative study of Hyptis suaveolens leaves antioxidant activity before and after essential oil extraction

Context: Hyptis suaveolens (L.) Poit; (Lamiaceae) is an aromatic plant whose leaves contain essential oils (less than 1%) and also non-volatile bio-active substances (More than 8%). However, after essential oil extraction, the leaf residues are generally poorly exploited. Which poses an efficient and optimal management problem for this natural resource. The valuation of these residues as substitute antioxidants is considerable. Methodology: After hydroethanolic (70/30; v/v) maceration of 100g of powder front and after extracting essential oil taken separately, a successively fractionate extract was obtained from solvents of increasing polarities. Next, the total polyphenols, flavonoids and tannins are determined. Finally, the antioxidant activities of extracts and fractions are evaluated by trapping the DPPH radical and then that of the ABTS radical. Results: The contents of total polyphenols and tannins decreased from 39.167±2.222 to 20.833±1.111 mg EAG/g and 8.733±0.156 to 6.500±0.267 respectively during essential oil extracting process. Still, the proportioning of total flavonoids gave more significant concentrations afterwards with 20.583±0.389 mg EQ/g against 15.417±0.222 mg EQ/g before. The antioxidant activity increased after extracting essential oil with TEAC value of 256.47 µm ol/L TE to 290.91 µm ol/L TE for ABTS method and IC50 value of 0.28mg / mL to 0.27 mg/mL for DPPH. Comparatively to ascorbic acid (IC50 = 0.05 mg/mL), Hyptis suaveolens leaves have moderate antioxidant activity. Conclusion: Hyptis suaveolens leaves have moderate antioxidant activity before and after essential oil extraction. The plant hydrodistillation residue could be used as a substitute antioxidant.Prospect: The determination of the molecular structures could increase the interest for these residues.