Phenolic profile, antioxidant and enzyme inhibitory activities of underutilized spices from Central Africa

The aim of the present study is to evaluate phytochemical profile, antioxidant and enzyme inhibitory activity of some underutilized Cameroon spice extracts, viz. The fruit of Xylopia africana, the fruit and the bulb of Aframomum sulcatum; and the bark of Hypodaphnis zenkeri. Four different solvent combinations were used for extraction of phytochemicals. Highest total polyphenol, flavonoid and tannin contents were observed in X. africana extract 10.32 ± 0.49 g gallic acid eq/100 g of dry matter, 146.66 ± 4.15 mg quercetin eq/100 g of dry matter, 452.44 ± 2.7 mg tannic acid eq/100 g spices dry matter. Methanol extracts revealed the presence of chlorogenic acid (0.790-4.312), vanillic acid (0.830-19.768), epicatechin (25.386-34.707), p-coumaric acid (1.127-12.652), protosynapic acid (0.221-186.562) and T-cinnamic acid (3.794-52.58) mg/100 g dry spice by HPLC analysis. Extracts of X. africana and H. zenkeri exhibited higher antioxidant activity: DPPH (182.24 ± 2.41 mg ascorbic acid eq/g dry spice), ABTS (9.247 ± 0.004 g trolox eq/100 g spice), hydroxyl free radicals (729.27 ± 3.07 mg mannitol eq/100 g spice) and reducing power (2.351 ± 0.002 g ascorbic acid equivalent/100 g spice). Positive and high correlations existed between the antioxidant activity of extracts obtained with different methods and their corresponding phenolic content. Extract of A. sulcatum highly inhibited porcine pancreatic lipase whereas, X. africana and H. zenkeri extracts highly inhibited α-amylase (98.82 and 99.54% respectively). These spices could be utilized as natural antioxidant sources for the management oxidative stress, lipid and carbohydrate metabolism related diseases.