Abstract
This study was aimed to phytochemically characterize and assess the antioxidant activities of 70% methanol extract and subsequent fractions of Cassia absus (L.) seeds, Gymnema sylvestre (L.) whole plant, Nigella sativa (L.) seeds, and Piper nigrum (L.) seeds. Powdered plant materials were extracted with 70% methanol and further fractionated with ethyl-acetate, n-butanol and the residual aqueous fraction. Phytochemical analysis was performed to detect different phytocompounds. Mineral compositions were quantified, and total phenolic and flavonoid contents were determined. The antioxidant potential of methanol extracts and fractions was assessed in vitro through estimating DPPH radical and superoxide anion scavenging activities and reducing power assay. Extraction yields ranging highest of N. sativa methanol extract (30.42�1.49%) and lowest of P. nigrum ethyl-acetate fraction (4.58�0.61%) were obtained. Results revealed that methanol extracts and fractions of selected plants contain phytocompounds such as alkaloids, flavonoids, phenols, glycosides, tannins, terpenoids, saponins, carbohydrates, fats and fixed oils. The mineral analysis showed considerable quantities of calcium (C. absus methanol extract: 372.454�3.633 mg/100g), magnesium (G. sylvestre methanol extract: 131.045�1.346 mg/100g), and zinc (N. sativa methanol extract: 36.019�0.284 mg/100 g) in all fractions while minor quantities of manganese, copper and cobalt were also found. Methanol extracts showed considerably higher total phenolic (N. sativa methanol extract: 179.71�2.14 mg GAE/g) and flavonoid (N. sativa methanol extract: 189.18�3.17 mg CE/g) contents compared to other fractions, and subsequently exhibited pronounced scavenging activities on DPPH* (N. sativa methanol extract: 23.8 �g/mL) and superoxide radicals (N. sativa methanol extract: 24.9 �g/mL) and had potent reductive abilities (N. sativa methanol extract: 1.123�0.038 O.D.). Conclusively, C. absus, G. sylvestre, N. sativa and P. nigrum possess significant nutritive properties and could be used as natural antioxidant sources to prevent oxidative stress-associated diseases.
Highlights
The use of medicinal plants as therapeutic remedies is as old as human civilization and people have been continuing to rely on them for primary healthcare needs [1]
Plant materials Gymnema sylvestre (Ghurmar boti) whole plant, seeds of Cassia absus (Chaksu), Nigella sativa (Kalonji) and Piper nigrum (Kali mirch) purchased from the local herbal store were identified by taxonomist of Department of Botany, University of Agriculture, Faisalabad, Pakistan, and herbarium No Cassia absus; 21213, Gymnema sylvestre; 21214, Nigella sativa; 21215 and Piper nigrum; 21216 were allotted for future reference
Methanolic extract of N. sativa gave the highest yield of 30.42±1.49%, whereas the ethyl-acetate fraction of P. nigrum gave the lowest yield (4.58±0.61%)
Summary
The use of medicinal plants as therapeutic remedies is as old as human civilization and people have been continuing to rely on them for primary healthcare needs [1]. 80% population of underdeveloped or developing countries still depends on natural-sourced products to cure their acute or chronic ailments [2]. It is currently estimated that more than 0.4 million plant species have been discovered. Compounds derived from natural sources have a significant contribution to the discovery of novel chemical entities. A multi-disciplinary approach is involved in the drug discovery process and is dependent upon many disciplines such as ethnobotany, biology, phytochemistry and chemical separation techniques. A considerable proportion (around 87%) of therapeutic agents is directly or indirectly derived from nature [3]
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