Seasonal and Circadian Study of a Thymol/γ-Terpinene/p-Cymene Type Oil of Ocimum gratissimum L. and Its Antioxidant and Antifungal Effects

Ocimum gratissimum oil is used for various medicinal, food and cosmetic applications due to its high chemical variability. Local businesses have considered the economic exploitation of this plant. A specimen sampled at São Luís, MA, Brazil, with thymol and derivatives oil, was subjected to seasonal and circadian study, and to antifungal and antioxidant assays. It was possible to observe that the weather conditions showed a direct influence on the oil yield and variation of its constituents, mainly oxygenated monoterpenes and monoterpene hydrocarbons, with the predominance of thymol, γ-terpinene, and p-cymene. Principal component analysis (PCA) was able to justify the oil chemical variability of the seasonal (70%) and circadian (86%) study. Oil displayed inhibition for the fungus Corynespora cassiicola at a concentration above 0.3 µL mL-1, and it showed a more significant activity by comparison to thymol. Using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay, the oil antioxidant activity was about 75% of thymol.

由于化学组成具有高度变异性，广圣罗勒（Ocimum gratissimum）精油被广泛应用于医药、食品及化妆品等多个领域，当地企业已考虑对该植物开展经济开发利用。研究人员针对从巴西马拉尼昂州圣路易斯市（São Luís, MA, Brazil）采集的该植物标本展开实验，该标本的精油中含有百里香酚（thymol）及其衍生物，实验涵盖季节节律与昼夜节律分析，以及抗真菌和抗氧化活性检测。研究结果显示，气象条件对精油得率及成分变化具有直接影响，其中受影响最为显著的成分为氧化型单萜类化合物与单萜烃类，该精油的优势成分为百里香酚、γ-松油烯（γ-terpinene）和对伞花烃（p-cymene）。主成分分析（PCA）可分别解释季节节律研究（70%）与昼夜节律研究（86%）中精油的化学变异性。当浓度高于0.3 µL·mL⁻¹时，该精油对菜豆棒孢叶斑病菌（Corynespora cassiicola）具有抑制活性，且其抗真菌效果相较于纯百里香酚更为显著。通过2,2-二苯基-1-苦基肼基（2,2-diphenyl-1-picrylhydrazyl, DPPH）自由基清除实验检测，该精油的抗氧化活性约为纯百里香酚的75%。