Phytochemical and heavy metal contents in Gnetum africanum (Welw. 1984) collected from three local markets in Lagos, Nigeria

Abstract

Gnetum africanum (Okazi leave) is an evergreen climbing vegetable which is highly priced in most regional markets in Nigeria. The present study examined the composition of phytochemicals (Alkaloids, Tannins, Flavonoids, Terpenes, Saponins, and Phenols) and heavy metals (Zinc, Lead, Copper, Cadmium, Chromium, Nickel and Arsenic) in G. africanum collected from three different markets (Iyana-Iba, Igando and Ikotun markets) in Lagos state, Nigeria. All analyses were done using standard analytical procedures. The highest dry weight of alkaloid (83.89±0.03mg/100g), flavonoid(108.75±1.11 mg/100g) and phenol(10.07±0.06 mg/100g) were obtained in G. africanum from Igando market; the peak tannins and saponins with values of 14.61±0.01 mg/100g and 4.08±0.00 mg/100g respectively were recorded in G. africanum from Ikotun market, while the highest dry weight for terpenes (23.64±0.03 mg/100g) was recorded in samples from Iyana-Iba market. On the contrary, the least dry weight for alkaloid(62.12±0.01mg/100g), phenol (6.22±0.00mg/100g), flavonoids (81.66±0.04 mg/100g) and terpenes (9.64±0.01 mg/100g) were recorded in samples from Ikotun market, while the least saponin (1.22±0.01 mg/100g), and tannins (7.95±0.03 mg/100g) were obtained from samples in Igando market. G. africanum from Iyana-Iba market possessed the highest wet weight value of alkaloids (62.07±0.01 mg/100g) and terpenes (15.99±0.03 mg/100g); samples of Ikotun market had highest wet weight in tannins (9.95±0.01 mg/100g) and saponin(3.33±0.03 mg/100g), while samples at Igando market had peak flavonoid and phenol (77.23±0.01 mg/100g, 7.12±0.01 mg/100g) wet weight respectively. All the levels of heavy metals (dry and wet weights) determined in the samples were not significantly different across the three markets (p>0.05). In conclusion, the secondary metabolites recorded in the leaves of Gnetum africanum indicated a good medicinal status while the heavy metal content in the leaves being below permissible limits indicated that the plants from the three markets is safe for consumption.