Abstract
Moringa oleifera (M. oleifera) leaves are rich in nutrients and antioxidant compounds that can be consumed to prevent and overcome malnutrition. The water infusion of its leaf is the easiest way to prepare the herbal drink. So far, no information is available on the antioxidant, antimutagenic, and antivirus capacities of this infusion. This study aimed to determine the composition of the bioactive compounds in M. oleifera leaf infusion, measuring for antioxidant and antimutagenic activity, and evaluating any ability to inhibit the SARS-CoV-2 main protease (Mpro). The first two objectives were carried out in vitro. The third objective was carried out in silico. The phytochemical analysis of M. oleifera leaf infusion was carried out using liquid chromatography-mass spectrometry (LC-MS). Antioxidant activity was measured as a factor of the presence of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The antimutagenicity of M. oleifera leaf powder infusion was measured using the plasmid pBR322 (treated free radical). The interaction between bioactive compounds and Mpro of SARS-CoV-2 was analyzed via molecular docking. The totals of phenolic compound and flavonoid compound from M. oleifera leaf infusion were 1.780 ± 5.00 µg gallic acid equivalent/g (µg GAE/g) and 322.91 ± 0.98 µg quercetin equivalent/g (µg QE/g), respectively. The five main bioactive compounds involved in the infusion were detected by LC-MS. Three of these were flavonoid glucosides, namely quercetin 3-O-glucoside, kaempferol 3-O-neohesperidoside, and kaempferol 3-α-L-dirhamnosyl-(1→4)-β-D-glucopyranoside. The other two compounds were undulatoside A, which belongs to chromone-derived flavonoids, and gentiatibetine, which belongs to alkaloids. The antioxidant activity of M. oleifera leaf infusion was IC50 8.19 ± 0.005 µg/mL, which is stronger than the standard butylated hydroxytoluene (BHT) IC50 11.60 ± 0.30 µg/mL. The infusion has an antimutagenic effect and therefore protects against deoxyribonucleic acid (DNA) damage. In silico studies showed that the five main bioactive compounds have an antiviral capacity. There were strong energy bonds between Mpro molecules and gentiatibetine, quercetin, undulatoside A, kaempferol 3-o-neohesperidoside, and quercetin 3-O-glucoside. Their binding energy values are -5.1, -7.5, -7.7, -5.7, and -8.2 kcal/mol, respectively. Their antioxidant activity, ability to maintain DNA integrity, and antimutagenic properties were more potent than the positive controls. It can be concluded that leaf infusion of M. oleifera does provide a promising herbal drink with good antioxidant, antimutagenic, and antivirus capacities.