Seasonal and circadian evaluation of a citral-chemotype from Lippia alba essential oil displaying antibacterial activity

In Brazil, the infusion from leaves of Lippin alba (Verbenaceae), popularly known as Erva-cidreira, is used for the treatment of infections, digestive disorders, cough, asthma, colds and anxiolytic, among others. It has been used in phytotherapy practices of communities of Santarem, Para State, Brazil, cultivated in a public program of medicinal plants and phytotherapy. In this work, the local influence of seasonality and planting time on essential oil yield and composition were evaluated, as well as in the development of a topical formulation to determine the oil efficacy in inhibition the Staphylococcus epidermidis strain. The plant was sampled during the dry and rainy seasons, three times a day, the oils extracted and its constituents identified by GC and GC-MS. The formulation of topical use was prepared with the incorporation of the oil (10%) to an anionic cream, followed by analysis of its organoleptic characteristics. The antibacterial activity of the topical formulation was evaluated by the Well Diffusion Method, using the S. epidermidis strain. The oil yield in the plant was from 2.2 to 4.3%, and its main constituents were geranial, neral, elemol, p-cymene, limonene, carvone, and geraniol, with the quantitative variation depending on the seasonality and the collection time. The results for the seasonal and circadian study were compatible with the data variance obtained by Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), with the formation of two distinct groups of primary constituents for the rainy and dry seasons. The formulated product maintained about 45% of the primary constituents of the oil (neral and geranial) for various days. It was homogeneous after centrifugation test, having shown excellent stability at 5 degrees C and 25 degrees C. Storage of the formulated product at higher temperatures appears to be a limiting factor for the antimicrobial action of the oil.