Abstract
Two commonly consumed spices in Nigeria—Piper nigrum (leaf and seed) and Monodora myristica (seed) were evaluated for natural antioxidant potentials in complementary in vitro assay systems. Extracts of the tested plant parts contained low amounts of antioxidant compounds: 4.00 - 6.65 μg GAE/mg and 2.50 - 10.38 μg RE/mg for phenols and flavonoids respectively. The extracts scavenged DPPH and hydroxyl radicals in the range of 4.32% - 37.37% (inferior to ascorbic acid and gallic acid used as standards) and 6.43% - 17.10% respectively. In the reducing power and phosphomolybdenum assays, the extracts showed ability to reduce Fe (III) and Mo (VI) ions to their lower valence states of Fe (II) and Mo (V) respectively, although these activities were inferior to those of the standards used. Comparatively, Monodora myristica seed extract was superior to Piper nigrum leaf and seed extracts in antioxidant potential, but all the extracts generally showed dose-dependent antioxidant activities. Evidently, the studied spice plants are not without some natural antioxidant capacity and would contribute appreciably in combating free radical damages when consumed.
Highlights
Plants are a valuable source of medicine and have helped in the maintenance of human health since time immemorial [1]
Monodora myristica seed extract was superior to Piper nigrum leaf and seed extracts in antioxidant potential, but all the extracts generally showed dose-dependent antioxidant activities
The seed extract of Monodora myristica had a mean total flavonoid content of 10.38 μg Rutin Equivalents (RE)/mg which was significantly higher (p < 0.01) than that of Piper nigrum leaf extract (2.50 μg RE/mg), while no flavonoid was detected in the Piper nigrum seed extract (Table 1)
Summary
Plants are a valuable source of medicine and have helped in the maintenance of human health since time immemorial [1]. They constitute an important source of active natural products which differ widely in terms of structures, biological properties and mechanisms of action [2]. Free radicals engage in electron pairing with important biological macromolecules in their quest for stable configuration. They cause damage to DNA, lipids, proteins, and co-factors of enzymes resulting in a number of pathological disturbances including cancer, atherosclerosis, cardiovascular diseases, ageing and inflammatory diseases [5,6].
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