Yeast extract and chitosan elicitation improves essential oil, regulates plant growth and antioxidative system in Lippia alba (Mill) N.E. Brown (Verbenaceae)

Lippia alba is one of the most used species in traditional medicine, having been the subject of intense exploration in search of the extraction of its essential oil, which contains several compounds of pharmacological importance. This study evaluated the effects of different concentrations of two biotic elicitors: yeast extract (YE) (0, 1, 2 and 4 g L−1) and chitosan (CH) (0, 1, 2 and 4 g L−1) in the accumulation of biomass, gas exchange, antioxidative system response, and production and profile of bioactive compounds (BCs). Foliar spraying with 4 g L−1 of CH favored the accumulation of shoot dry biomass and significantly increased the levels of chlorophyll a and carotenoids. Both elicitors were efficient to increase the essential oil content extracted from the leaves of L. alba and, in general, the elicitors tested at concentrations of 2 and 4 g L−1 showed the highest amounts of BCs and glandular trichome density. Chemical analysis of BCs revealed 46 different compounds, with Geranial and Geraniol being the main components. The application of YE induced the production of an exclusive compound (Trans-piperitol), while CH induced the formation of seven exclusive compounds (Santolina triene, Myrcenol, Neral, Cis-Pinocarvyl acetate, Dimethoxy-(Z)-citral, Geranyl acetate and Limonene aldehyde). Yeast extract and Chitosan proved to be efficient to increase the BCs content in Lippia alba, however, the application of 4 g L−1 of CH resulted in a higher production of shoot dry biomass, photosynthetic parameters, in the density of glandular trichomes and in the production of BCs.