Immunomodulatory activities of methanolic extract and isolated compounds from the leaves of Combretum aculeatum Vent

Popularly known as Lahugni in Fulfuldeh and Karkarbaw in Tupuri, Combretum aculeatum Vent. is used in traditional medicine in the Northern regions of Cameroon as back pain, muscular-skeletal aches and eyes remedies; it is also used for the treatment of blennorrhoea, leprosy, rheumatic pains and other inflammatory diseases. This study was conducted to evaluate the immunomodulatory effect of crude methanolic extract and isolated compounds from C. aculeatum using luminol/zymosan and lucigenin/MPA based chemiluminescence assay. Isolation of secondary metabolites from the leaves of C. aculeatum was done by the means of usual chromatographic techniques and their structures were confirmed on the basis of spectroscopic data and those available in literature. The first phytochemical exploration of the leaves of C. aculeatum afforded s-sitosterol (1) and its glucoside (2), oleanolic acid (3), maslinic acid (4), corosolic acid (5), alphitoli cacid (6), arjunolic acid (7), asiatic acid (8), 3,3’-di-O-methylellagic acid (9) and 3,3’,4-tri-O-methylellagic acid-4’-O-D-glucopyranoside (10) (Figure 1). To the best of our knowledge, all these compounds are isolated and reported for the first time from this plant and, alphitolic acid is characterized for the first time from the genus Combretum. This study also demonstrated potent immunomodulatory activities of methanolic extract and compounds 3, 4, 5 and 9 in both luminol and lucigenin enhanced chemiluminescence assay compare to ibuprofen used as reference. These results are in agreement with the enthnobotanical uses of the plant and some previous reports on pharmacological activities such as anti-inflammatory, antioxidant, anticancer effects of some isolates and their related previously isolated and identified from several plants.