Evaluation of antioxidant and antacid activities of <i>Globimetula braunii</i> and <i>Parquetina nigrescens</i> extracts

Natural products are one of the best sources of therapeutic-based compounds for the treatment of peptic ulcer, which denotes open sores on the lining of the stomach or small intestines. Globimetula braunii (Family Loranthaceae), Microdesmis puberula (Family Pandaceae) and Parquetina nigrescens (Family Apocynaceae) have been documented for various medicinal uses, including the traditional treatment of peptic ulcer in Nigeria. This study aimed to assess the antioxidant and antacid properties of Globimetula braunii, Microdesmis puberula and Parquetina nigrescens. The plant samples were collected, identified and authenticated. The samples were allowed to air dry, pulverised and then extracted using methanol. The extracts were assessed for antioxidant (2,2-diphenyl-1-icrylhydrazyl, DPPH), free radical scavenging activity, total phenolic content (TPC), total flavonoid content (TFC), and antacid activity. The total phenolic content was highest in G. braunii, followed by P. nigresens and then M. puberula with values of 6.74 mg GAE/g, 3.35 mg GAE/g and 0.56 mg GAE/g, respectively. The crude extract of G. braunii showed the highest radical scavenging activity below 50% with IC₅₀ value of 53.73. Globimetula braunii methanol extract (250 mg/250mL) showed the highest artificial gastric acid neutralising activity by raising the pH of the artificial gastric acid from 1.2 to 1.80±0.04, which is like the standard NaHCO₃ (100 mg/250mL) that raised the pH of the artificial gastric acid from 1.2 to 1.78±0.03. The results from this study support the ethnomedicinal claims that plants can be used in the management of peptic ulcer, and these plants could serve as sources of lead compounds to produce natural antacids.