Water activity studies with total phenols and total antioxidant properties of sun dried, grated and stored Vernonia amygdalina leaves

Abstract

Vernonia amygdalina leaves are widely utilized as food additive and for many herbal preparations in Nigeria. This study investigated the total phenols content and antioxidant properties of raw, processed and stored Vernonia amygdalina leaves. Processing methods used in this study entailed sun drying and grating. Storage conditions were in the open laboratory and at water activities (a_w) of 0.23, 0.52 and 0.97. All storages were carried out at ambient conditions and Storage duration was two months. All investigations carried out were in accordance with standard methods. The results indicated that in raw Vernonia amygdalina leaves, the total phenol content was 3.10±0.94mg/g and percentage antioxidant activity was 96.31±2.05%. It was further discernable from the results that processing and storage led to increases in total phenol contents, while there was a reduction of percentage antioxidant activity. Statistically, the storage changes observed with phenol determinations were at P<0.05 found to be significant. Furthermore, at P<0.05, the reduction in percentage antioxidant activity following processing and storage were statistically significant. These findings would be useful in the formulation of standard methods for the handling of Vernonia amygdalina leaves.