Biomedical Potential of Natural Products from Selected Tanzanian Flora: A Review

Abstract

Natural products have been used for treatment of various diseases for thousands of years and served as sources of drug lead compounds for the improvement of livelihood. This paper presents a review on the biomedical potentials of selected natural products isolated from eight plant species indigenous to Tanzania. The review covers research work published between 2010 and 2023, and identifies 33 natural products with different pharmacological properties from Tanzanian plants. These bioactive natural products are discussed with other similar compounds isolated elsewhere from the same or different plant species to get further insights on the potential application in modern medicine based on information obtained from online search from different databases including Chemical Abstract, Google Scholar, MEDLINE, PubMed and Science Direct using different key words or phrases. The review includes antitubercular, anticancer and neuroprotective flavonoids from Erythrina schliebenii (Fabaceae), antitubercular and antioxidant metabolites from three mangrove species Heritiera littoralis (Sterculiaceae), Xylocarpus granatum (Meliaceae) and Sonneratia alba (Lythraceae). The review also covers antiplasmodial secoiridoids and iridoids from Morinda asteroscepa (Rubiaceae), antibacterial biflavonoids from two Ochna species (Ochnaceae), antiviral and antiplasmodial diterpenoids from Croton kilwae (Euphorbiaceae), and other constituents from these plant species. Most of these plants are rare, endemic or near endemic in Tanzania. Of these natural products, the catechinoid 13 (IC₅₀ 4.5 µg/mL) was four times more active than the positive control towards radical scavenging, the biflavonoid 31 (MIC 2.2 μM) was more potent in antibacterial assay than the standard drug, whereas diterpenoids 34-36 demonstrated strong anti-proliferative effect against the malaria parasite Plasmodium falciparum (80-100%, at 50 μM), making them promising candidates for drug development. The review argues about challenges associated with the realization of the full potential of biomedical agents such as scalability, toxicity, solubility, and bioavailability thereby calling for concerted research endeavors to address them to exploit effusively the potential that resides in the natural products towards drug development. The mode of actions of the lead compounds must be elucidated and clinical studies conducted for targeted disease treatments.

Tanzanian flora; antiplasmodial; anticancer; antioxidant; antiviral; antibacterial; neuroprotective; anti-inflammatory