Unidad de Biotecnología, Centro de Investigación Científica de Yucatán, Mérida, Yucatán, Mexico.
Centro de Investigación Biomédica del Sur - IMSS, Xochitepec, Morelos, Mexico.
J Ethnopharmacol. 2019 Oct 28;243:112081. doi: 10.1016/j.jep.2019.112081. Epub 2019 Jul 15.
Wild basil (Ocimum campechianum Mill.), an aromatic herb of the Lamiaceae family known as "albahaca de monte" (Spanish) or "x'kakaltun" (Mayan) in Yucatan, is used in Mayan traditional medicine to treat diabetes, as well as to alleviate fever symtoms, stomach pain, conjunctivitis, and various skin affections.
To isolate and identify the bioactive metabolites responsible for the α-glucosidase inhibitory activity previously detected in the leaf infusion O. campechianum.
The bioassay-guided fractionation and purification of the lyophilized infusion was carried out using a liquid-liquid partition procedure, followed by successive chromatographic purifications of the semipurified fractions. The isolated metabolites were identified by comparing their spectroscopic data with those reported in the literature. The liophylized infusion, together with the semipurified fractions, and the pure metabolites were tested for their antioxidant and α-glucosidase inhibitory activities, as well as their antihyperglycemic effect.
Chromatographic purification of the semipurified fractions led to the isolation of the polymethoxylated flavones 5-demethyl nobiletin (1) and 5-demethyl sinensetin (2), together with luteolin (3), methyl rosmarinate (4) and rosmarinic acid (5). Metabolites 4 and 5 appear to be responsible for the α-glucosidase inhibitory activity and the antihyperglycemic effect detected in the lyophilized infusion. A Lineweaver-Burk double reciprocal plot confirmed that the higher α-glucosidase inhibitory activity of 4 is of non-competitive nature. Both 4 and 5 caused a decrease in blood glucose higher than that caused by acarbose, a result that appears to be related to their strong α-glucosidase inhibitory activity. Even though flavonoids 1-3 did not show a good inhibition of α-glucosidase, these products decreased blood glucose in the in vivo model, suggesting a different antihyperglycemic mechanism.
The results confirm both the traditional use of O. campechianum and the importance of the leaf infusion as a potential source of antihyperglycemic agents. The isolation of 5-demethyl nobiletin (1) and 5-demethyl sinensetin (2) from O. campechianum and other Ocimum spp. suggests that polymethoxyflavones can be considered chemotaxonomical markers for the genus.
野生罗勒（Ocimum campechianum Mill.），唇形科的一种芳香草本植物，在尤卡坦被称为“阿尔巴恰卡”（西班牙语）或“X'kakaltun”（玛雅语），在玛雅传统医学中用于治疗糖尿病，以及缓解发烧症状、胃痛、结膜炎和各种皮肤疾病。
从叶浸膏 O. campechianum 中分离并鉴定出先前检测到具有α-葡萄糖苷酶抑制活性的生物活性代谢物。
使用液-液分配程序对冻干浸膏进行生物活性指导的分步分离和纯化，然后对半纯化馏分进行连续色谱纯化。通过比较其光谱数据与文献中的数据来鉴定分离出的代谢物。对冻干浸膏、半纯化馏分和纯代谢物进行抗氧化和α-葡萄糖苷酶抑制活性以及抗高血糖作用的测试。
半纯化馏分的色谱纯化导致分离出多甲氧基黄酮 5-去甲基诺必灵（1）和 5-去甲基新诺必灵（2），以及木犀草素（3）、甲基迷迭香酸（4）和迷迭香酸（5）。代谢物 4 和 5 似乎是冻干浸膏中检测到的α-葡萄糖苷酶抑制活性和抗高血糖作用的原因。Lineweaver-Burk 双倒数作图证实，4 的更高的α-葡萄糖苷酶抑制活性是非竞争性的。4 和 5 均导致血糖降低，高于阿卡波糖的作用，这一结果似乎与它们较强的α-葡萄糖苷酶抑制活性有关。尽管黄酮 1-3 对α-葡萄糖苷酶没有很好的抑制作用，但这些产物在体内模型中降低了血糖，表明存在不同的抗高血糖机制。
结果证实了 O. campechianum 的传统用途以及叶浸膏作为抗高血糖药物潜在来源的重要性。5-去甲基诺必灵（1）和 5-去甲基新诺必灵（2）从 O. campechianum 和其他 Ocimum spp. 的分离表明，多甲氧基黄酮可以被视为该属的化学分类标记。
