Department of Biochemistry, Faculty of Science, University of Johannesburg, Auckland Park Kingsway Campus, Johannesburg, South Africa.
Malar J. 2024 May 11;23(1):141. doi: 10.1186/s12936-024-04976-1.
The development of resistance by Plasmodium falciparum is a burdening hazard that continues to undermine the strides made to alleviate malaria. As such, there is an increasing need to find new alternative strategies. This study evaluated and validated 2 medicinal plants used in traditional medicine to treat malaria.
Inspired by their ethnobotanical reputation of being effective against malaria, Ziziphus mucronata and Xysmalobium undulutum were collected and sequentially extracted using hexane (HEX), ethyl acetate (ETA), Dichloromethane (DCM) and methanol (MTL). The resulting crude extracts were screened for their anti-malarial and cytotoxic potential using the parasite lactate dehydrogenase (pLDH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, respectively. This was followed by isolating the active compounds from the DCM extract of Z. mucronata using silica gel chromatography and structural elucidation using spectroscopic techniques (NMR: H, C, and DEPT). The active compounds were then targeted against P. falciparum heat shock protein 70-1 (PfHsp70-1) using Autodock Vina, followed by in vitro validation assays using ultraviolet-visible (UV-VIS) spectroscopy and the malate dehydrogenase (MDH) chaperone activity assay.
The extracts except those of methanol displayed anti-malarial potential with varying IC values, Z. mucronata HEX (11.69 ± 3.84 µg/mL), ETA (7.25 ± 1.41 µg/mL), DCM (5.49 ± 0.03 µg/mL), and X. undulutum HEX (4.9 ± 0.037 µg/mL), ETA (17.46 ± 0.024 µg/mL) and DCM (19.27 ± 0.492 µg/mL). The extracts exhibited minimal cytotoxicity except for the ETA and DCM of Z. mucronata with CC values of 10.96 and 10.01 µg/mL, respectively. Isolation and structural characterization of the active compounds from the DCM extracts revealed that betulinic acid (19.95 ± 1.53 µg/mL) and lupeol (7.56 ± 2.03 µg/mL) were responsible for the anti-malarial activity and had no considerable cytotoxicity (CC > µg/mL). Molecular docking suggested strong binding between PfHsp70-1, betulinic acid (- 6.8 kcal/mol), and lupeol (- 6.9 kcal/mol). Meanwhile, the in vitro validation assays revealed the disruption of the protein structural elements and chaperone function.
This study proves that X undulutum and Z. mucronata have anti-malarial potential and that betulinic acid and lupeol are responsible for the activity seen on Z. mucronata. They also make a case for guided purification of new phytochemicals in the other extracts and support the notion of considering medicinal plants to discover new anti-malarials.
疟原虫耐药性的发展是一个令人担忧的问题，它继续破坏缓解疟疾的进展。因此，人们越来越需要寻找新的替代策略。本研究评估和验证了两种用于治疗疟疾的传统医学药用植物。
受其作为抗疟有效植物的民族植物学声誉的启发，我们收集了枣（Ziziphus mucronata）和黄华（Xysmalobium undulatum），并分别使用正己烷（HEX）、乙酸乙酯（ETA）、二氯甲烷（DCM）和甲醇（MTL）进行连续提取。使用寄生虫乳酸脱氢酶（pLDH）和 3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四唑溴化物（MTT）测定法分别评估粗提物的抗疟和细胞毒性潜力。然后，使用硅胶色谱法从 Z. mucronata 的 DCM 提取物中分离活性化合物，并使用光谱技术（NMR：H、C 和 DEPT）进行结构鉴定。然后，使用 Autodock Vina 将活性化合物靶向疟原虫热休克蛋白 70-1（PfHsp70-1），然后使用紫外-可见（UV-VIS）光谱和苹果酸脱氢酶（MDH）伴侣活性测定法进行体外验证试验。
除甲醇提取物外，其余提取物均表现出不同的 IC 值的抗疟潜力，枣正己烷（11.69±3.84μg/mL）、乙酸乙酯（7.25±1.41μg/mL）、DCM（5.49±0.03μg/mL）和黄华正己烷（4.9±0.037μg/mL）、乙酸乙酯（17.46±0.024μg/mL）和 DCM（19.27±0.492μg/mL）。除 Z. mucronata 的 ETA 和 DCM 提取物的细胞毒性较小（CC 值分别为 10.96 和 10.01μg/mL）外，其他提取物均表现出最小的细胞毒性。从 DCM 提取物中分离和结构鉴定活性化合物表明，白桦脂酸（19.95±1.53μg/mL）和羽扇豆醇（7.56±2.03μg/mL）是抗疟活性的原因，且没有明显的细胞毒性（CC>μg/mL）。分子对接表明 PfHsp70-1、白桦脂酸（-6.8kcal/mol）和羽扇豆醇（-6.9kcal/mol）之间具有很强的结合。同时，体外验证试验表明，这些化合物破坏了蛋白质结构元素和伴侣功能。
本研究证明黄华和枣具有抗疟潜力，白桦脂酸和羽扇豆醇是枣中活性成分的来源。它们还支持对其他提取物进行新植物化学物质的引导纯化，并支持从药用植物中发现新抗疟药物的观点。
