Secondary metabolite production by plants is influenced by external environmental factors that can change depending on the seasons, which makes it important to know how the plant, through its metabolism, is able to adapt to these variations. Mentha x villosa and Plectranthus amboinicus present in their chemical composition polyphenols, and through previous studies, it has been seen that these two species present promising in vitro photoprotective activity. The aim of this study was to evaluate seasonal alterations in photoprotective and antioxidant activities and the influence of factors such as precipitation levels and sun radiation incidence. Thus, polyphenol quantification, cromatographics (HPLC-DAD) and multivariate (PCA) analyses of extracts of the two species through twelve months were done. It was observed that the best months for photoprotective and antioxidant activities were September for M. villosa and July for P. amboinicus (SPF = 14.79). It was possible to conclude that solar radiation more clearly influences the production of phenolics and the increase of SPF in M. villosa, in addition to favoring the antioxidant activity of the two species, while precipitation seems to have no influence.

中文翻译：

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两种菊科植物多酚含量，防晒因子和抗氧化活性的季节性变化

植物的次生代谢产物生产受外部环境因素的影响，外部环境因素会根据季节而变化，因此了解植物如何通过其新陈代谢适应这些变化非常重要。薄荷x绒毛和侧柏在它们的化学组成中存在多酚，并且通过先前的研究，已经发现这两个物种呈现出有希望的体外光保护活性。这项研究的目的是评估光防护和抗氧化活性的季节性变化以及诸如降水量和太阳辐射发生率等因素的影响。因此，在十二个月内对这两种物种的提取物进行了多酚定量，色谱（HPLC-DAD）和多变量（PCA）分析。据观察，对光防护和抗氧化活性最好的月份是毛绒球菌（M. villosa）为9月，而竹子假单胞菌（P. amboinicus）为7月。（SPF = 14.79）。可以得出这样的结论：除了有利于两个物种的抗氧化活性外，太阳辐射还更明显地影响毛细支气管菌中酚类的产生和SPF的增加，而降水似乎没有影响。