Seasonal Chemical Variability of Aloysia polystachya Leaves

Abstract

The use of natural products as food ingredients requires adequate regulation and safety assessment for its legal commercialization. Aloysia polystachya (Griseb.) Moldenke, Verbenaceae, is a native plant from Argentina with aromatic and medicinal properties. A selected Argentinean genotype of this species was harvested and evaluated monthly for 1 year involving the different stages of a whole crop cycle to determine its chemical variability. The volatile and non-volatile fractions of its air-dried leaves were characterized. The content of total polyphenols, spectrophotometrically estimated by the Folin-Ciocalteu method, varied from 4.2 to 6.2% gallic acid equivalents. Verbascoside identification was confirmed by HPLC-MS/MS, and its content was evaluated by HPLC with a multiple wavelength detector, ranging from 2.2 to 5.4%. Volatile oil yield obtained by hydrodistillation was calculated in each sample, and their chemical compositions were determined by GC-FID-MS. The yield values ranged from 1.5 to 6.6% being rich in carvone (62.3–81.9%) and limonene (12–32.7%). The contents of verbascoside, polyphenols, and volatile oil fluctuated throughout the year. The most suitable profile was found from September to December. This work is a contribution to the standardization and quality control of A. polystachya to be used for food or medicinal purposes.