Seasonal Chemical Variability and Antimicrobial, Anti-Proliferative Potential of Essential Oils from Baccharis uncinella, B. retusa, and B. calvescens (Asteraceae)

Essential oils (EOs) of three native species <i>Baccharis uncinella</i>, <i>B. retusa</i> and <i>B. calvescens</i>, obtained through hydrodistillation, were analyzed by GC-MS and GC-FID for seasonality, and the antimicrobial and anti-proliferative activities were evaluated. EO of <i>B. calvescens</i> and <i>B. uncinella</i> consisted mainly of oxygenated sesquiterpenes, while in the EO of <i>B. retusa</i>, monoterpene hydrocarbons were predominant. The highest antimicrobial activity was observed for spring <i>B. uncinella</i> EO against <i>S. aureus</i>, <i>C. albicans</i> and summer <i>B. uncinella</i> EO against <i>C. albicans</i> and <i>B. subtilis</i>. Essential oils of <i>B. calvescens</i> showed more effective anti-proliferative activity than <i>B. retusa</i> EO and <i>B. uncinella</i> EO. This is the first study of the EO of <i>B. retusa</i>, and it was demonstrated that the majority composition was different in all seasons of the year, justifying the importance of the seasonal study. Furthermore, the summer and spring EO showed potent cytostatic effects against the K562 and OVCAR-03 cell lines, respectively. For each species, PCA differentiated the EO chemical composition seasonally. PCA of all samples distinguished the three species. This study underscores the importance of assessing seasonal variation in the chemical composition and biological activities of essential oils, highlighting the potential of compounds spathulenol, caryophyllene oxide, limonene and α-pinene for achieving the desired product properties.