Plants have been known to be of medicinal use in many societies and cultures around the globe. They have served and still serve as alternatives for conventional medicine in homes as natural remedies for infections, inflammations and noncommunicable diseases such as diabetes mellitus, gout, and hypertension. In other circumstances induction of labour has been achieved by plants. Elsewhere, Marantodes pumilum (Blume) Kuntez is commonly used to treat parturition, flatulence, dysentery, dysmenorrhoea, gonorrhoea, and bone diseases (7).
Recently, there has been an increased interest in use of plant-based remedies either to find new drugs, employ cheaper sources of medicine, or even to take advantage of the claimed safety in plants (4, 14). The use of plants as medicine has been done either through food, or special preparations such as infusions, smoothies, decoctions, or poultices. Therefore, many edible plants are part of the search for alternative medicines. However, there are still many plants whose mechanism of action is known (30).
Plants are also used as raw materials for pharmaceutical products. A major interest has been in the plant phytochemistry and their natural oils. Xanthine oxidase (XO) is a key enzyme in formation of uric acid from degradation of purine nucleotides in the last step of in humans. XO is associated with inflammation through production of free radicals. During re-oxidation of XO, molecular oxygen acts as an electron acceptor, producing superoxide radical (O2−) and hydrogen peroxide (H2O2). XO is part of an important biological source of superoxide radicals (33). Under favourable conditions especially when XO is overproduced, uric acid can crystallise in arthrosis (joints) and kidneys and cause inflammation known as arthritis or gout and renal calculi respectively. Uric acid is a marker for gout and several haemodynamic abnormalities (7).
Xanthine oxidase is a therapeutic target for Allopurinol and Febuxostat, the commonly available xanthine oxidase inhibitors (XOI). Xanthine oxidase inhibitors are associated with side effects including Steven Johnson Syndrome, fever, skin rash, eosinophilia, hepatitis, and renal toxicity (19). Both of these drugs are expensive, inaccessible to some developing countries. Such unmet medical needs and health hazards posed by these drugs require more effort in finding novel Xanthine oxidase inhibitors that are much effective and have a good safety profile. These findings indicate the necessity for the development and discovery of more precise Xanthine oxidase inhibitors aimed at improving the treatment of gout and a reduction of complications that arise due to hyperuricemia while realising fewer adverse effects profile (19). The use of plant-based products may be very efficient as they are easily available and generally safe for biological systems (30). Musa sapientum L is one of the species in the banana family, and is one of the common fruits in the world. Nearly all parts of a banana tree are commonly used as traditional medicine for treating diarrhoea, menorrhagia, diabetes, dysentery, and antiulcerogenic, hypoglycaemic, antilithic, hypolipidemic conditions, plus antioxidant actions, inflammation, pains and even snakebites (1).
Malus pumila is largely cultivated around the world in temperate regions. It is usually eaten as a fruit and flowers can be used as tea. Studies have demonstrated that the plant contains some medicinal properties which can be targeted against ageing, oxidative stress, cancers, and bacterial infections. The chemical constituents of M. pumila include flavonoids, terpenoids and organic acids. Its main chemical components are dihydrochalcone such as phlorizin, phloretin, and other flavonoids such as quercetin, kaempferol and rutin (17).
Annona senegalensis is commonly called wild custard apple, used as food or a food additive as all parts of the plant contain varying amounts of essential oils. According to some study, it contains major bioactive constituents including tannins, flavonoid, saponins, alkaloids, glycosides, steroids, volatile acids and anthocyanin (20). It has also been reported in literature that the plant contains various minerals such as calcium, potassium, magnesium, zinc, copper, manganese as well as ascorbic acid and amino acids which makes it an important source of nutrients. The roots, root bark and leaves have been reported to have been used to treat malaria, tuberculosis (6, 20).
Annona senegalensis is used for both food and medicinal purposes. It has also been reported in literature that different parts of the plant are employed in traditional medicine and home remedies to cure some diseases such as tuberculosis, hernia, diabetes, gastritis, male sexual impotence, difficulty in swallowing, and snake bites (18). Annona senegalensis has also been reported to have anti-cancer properties (5). Again, some researchers reported on the potential of A. senegalensis in the treatment of a minimum of three COVID 19 symptoms such as cough, fever, myalgia, and the treatment of liver, breast, and colon cancers (18). In this study, aqueous extracts of Musa sapientum and Malus pumila peels, and A. senegalensis root bark were investigated for the inhibitory potential on xanthine oxidase activity.