A fast and specific reversed-phase high-performance liquid chromatography (HPLC) method was used for the immediate identification of flavonoids (gallic acid, rutin, quercetin, ascorbic acid, and kaempferol) in the leaves extract of Mangrove (Rhizophora apiculata). The R. apiculata has lots of valuable medicinal properties including antiallergic, anti-inflammatory, antimicrobial, antiviral, antioxidant, vascular antitumor activity, and enzyme inhibition; however, the activity of antioxidant is perhaps the greatest studied property attributed to flavonoids. Magnetic stirrer was used for the pretreatment process of sample with methanol by using a temperature of 50°C for 40 min, followed by separation on column size 250 mm 4.6 mm (5 μm) Hypersil Gold C18 (Thermo Electron Corporation) with water–methanol–acetonitrile (45:40:15 v/v/v) containing acetic acid 1.0% as a mobile phase. Moreover, 254-nm wavelength was used to detect the extract. The standard retention times (Rt) of gallic acid, rutin, ascorbic acid, quercetin, and kaempferol were found to be 2.610, 2.875, 3.150, 5.789, and 8.983, respectively. The existence of gallic acid, rutin, ascorbic acid, kaempferol, and quercetin in Mangrove leaves extract was found matching according to the standard retention time. In Mangrove leaves, gallic acid was found to have the retention time at 2.538, rutin at 2.873, quercetin at 5.796, and kaempferol at 8.976. However, the ascorbic acid was not identified. The amount of rutin, gallic acid, quercetin, and kaempferol was calculated by using the assay formula. In Mangrove leaves, the amount of gallic acid, rutin, quercetin, and kaempferol is 3.024, 5.485, 5.144, and 8.361%, respectively.
