Resumo:
The present study describes the seasonal and circadian variations of the major compounds
from Lippia alba leaves. SPSS was used to identify, quantify, and associate the variations in
the secondary metabolites of this species through HPLC/DAD analysis of the leaves
hydroethanolic extracts of six selected L. alba specimens. For the circadian study, the samples
were collected at four different daily hours in each year's season. For the seasonal study, the
samples were collected monthly from the same individuals for two consecutive years (2018
and 2019). These samples were analyzed and quantified using a validated HPLC method for
flavonoids, iridoids, and phenylpropanoids. Mussaenoside, acteoside, and tricin-7-Odiglucuronide showed a moderate positive correlation between their biosynthesis and the
precipitation index, while epi-loganin had a moderate negative correlation. Acteoside showed
a moderate positive correlation between the minimum registered temperature and its
production. Compared with previous studies, a drastic reduction (about 95%) in the
production of tricin-7-O-diglucuronide compared with previous study and this difference
could be attributed to the plant's aging. Thus, the data demonstrated that lower temperatures
and high rainfall could favor the production of the major L. alba active compounds (acteoside
and tricin-7-O-diglucuronide) and that older plants harm their production.
