Laboratory of Applied Biochemistry, Department of Biological Sciences, Faculty of Science, University of Ngaoundere, PO Box 454, Ngaoundere, Cameroon.
ANDI Centre of Excellence for Onchocerciasis Drug Research, Biotechnology Unit, Faculty of Science, University of Buea, PO Box 63, Buea, Cameroon.
Acta Parasitol. 2023 Sep;68(3):566-581. doi: 10.1007/s11686-023-00686-x. Epub 2023 Jun 19.
Onchocerciasis is a neglected tropical disease that remains endemic in sub-Saharan African countries. Unfortunately, only a few microfilaricidal agents have been approved so far. This study aimed to assess the in vitro macro and microfilaricidal potentialities of the hydro-methanolic extracts of the different powdery fractions of Khaya senegalensis against Onchocerca ochengi.
Adult male worms and microfilariae (mf) of O. ochengi were isolated from cowhides in Ngaoundere II, Cameroon. Parasites were incubated for 4 h (mf) or 48 h (adult worms) in RPMI-1640 medium in the presence or absence of ivermectin, flubendazole, or hydro-methanolic extracts of different plant powdery fractions obtained by controlled differential sieving. The filaricidal effect was evaluated using motility (mfs) and mortality tests (worms) and oxidative stress parameters. Cytotoxicity and acute toxicity tests were performed on monkey-derived kidney cell lines (LLC-MK2) and Swiss albino mice, respectively, and selectivity indexes were determined. Phytochemical screening was also carried out using high-performance liquid chromatography/UV (HPLC/UV), molecular networking, and through quantification of phenolic contents.
The hydro-methanolic extracts of 0-63 µm fractions from leaves and barks exhibited the strongest macrofilaricidal activities with lethal concentrations 50 of 162.4 and 208.8 µg/mL respectively versus 22.78 µg/mL for flubendazole. These two fractions also showed the fastest microfilaricidal activities (T of 1 h), although it was low when compared to ivermectin (T < 1 h). Their macrofilaricidal effects were accompanied by a significant inhibition of nitric oxide secretion and a significant increase of glutathione and catalase activity compared to the untreated group. However, no effect was found on superoxide dismutase activity, the GABAergic and glutamatergic receptors. Although neither extract was toxic to Swiss mice until a dose of 2000 mg/kg body weight, the 0-63 µm leaf fraction hydro-methanolic extract was selectively more effective on worms than bark extract (SI = 1.28 versus 0.34). Both extracts were found to contain some flavonoids including procyanidin-, rutin-, myricetin-, and naringenin derivatives as well as new unknown compounds. However, the total polyphenol, flavonoid and tannin contents of the leaf extract were significantly greater (P < 0.05) than that of the bark extract.
These results support the anti-filarial effect of K. senegalensis leaves and highlight stress oxidative markers as new therapeutic targets in O. ochengi. Further, in vivo experiments are required in understanding their anti-parasitic properties, and testing combinations of fine fractions.
盘尾丝虫病是一种被忽视的热带病，仍在撒哈拉以南非洲国家流行。不幸的是，迄今为止，只有少数几种杀微丝蚴药物获得批准。本研究旨在评估不同粉末状 Khaya senegalensis 提取物的水-甲醇提取物对奥氏曼森线虫的体外大、微杀幼虫潜力。
从喀麦隆恩冈代雷二世的牛皮中分离出奥氏曼森线虫的成年雄性蠕虫和微丝蚴（mf）。在 RPMI-1640 培养基中，将寄生虫孵育 4 小时（mf）或 48 小时（成年蠕虫），同时存在或不存在伊维菌素、氟苯达唑或不同植物粉末部分的水-甲醇提取物，这些提取物通过控制差异筛分获得。使用运动性（mf）和死亡率测试（蠕虫）和氧化应激参数评估杀幼虫作用。在猴衍生的肾细胞系（LLC-MK2）和瑞士白化小鼠上分别进行细胞毒性和急性毒性试验，并确定选择性指数。还使用高效液相色谱/紫外线（HPLC/UV）、分子网络和通过酚含量定量进行植物化学筛选。
叶片和树皮的 0-63µm 粉末部分的水-甲醇提取物表现出最强的大杀幼虫活性，其致死浓度 50 分别为 162.4µg/mL 和 208.8µg/mL，而氟苯达唑为 22.78µg/mL。这两个部分还表现出最快的微杀幼虫活性（T 为 1 小时），尽管与伊维菌素相比（T<1 小时）较低。与未处理组相比，它们的大杀幼虫作用伴随着一氧化氮分泌的显著抑制和谷胱甘肽和过氧化氢酶活性的显著增加。然而，在超氧化物歧化酶活性、γ-氨基丁酸能和谷氨酸能受体上没有发现任何影响。尽管直到 2000mg/kg 体重的剂量，两种提取物都对瑞士小鼠均无毒性，但叶片的 0-63µm 水-甲醇提取物对蠕虫的选择性比树皮提取物更有效（SI=1.28 对 0.34）。两种提取物都含有一些类黄酮，包括原花青素、芦丁、杨梅素和柚皮素衍生物以及新的未知化合物。然而，叶片提取物的总多酚、类黄酮和单宁含量明显高于（P<0.05）树皮提取物。
这些结果支持 K. senegalensis 叶片的抗丝虫作用，并强调氧化应激标志物作为奥氏曼森线虫的新治疗靶点。此外，还需要进行体内实验来了解它们的抗寄生虫特性，并测试精细部分的组合。
