Phenolic Profiling of Avocado Leaf Extracts

Phenolic compounds present in the fermented and non-fermented avocado leaf extracts were analysed using an Acquity Ultra Performance Liquid Chromatography (UPLC) system (Waters Corporation, Milford, MA, USA) coupled to an electrospray ionization (ESI) source operating in the negative mode and a mass detector time of flight (TOF) micro mass spectrometer (Waters). The compounds of interest were separated on an ACQUITY UPLC BEH Shield RP18 column (1.7 μm, 2.1 × 100 mm; Waters Corporation, Milford, MA, USA) at 40 °C using the conditions and gradient previously stated [31 (link)]. H₂O acidified with 1% of acetic acid and acetonitrile were used as phase A and B, respectively. Analyses were performed in triplicate. The identification of the phenolic compounds was made according to the literature. For ensuring the mass accuracy, the tolerances chosen had a score higher than 90% and error lower than 5 ppm. To quantify the phenolic compounds identified in the avocado leaf extracts, calibration curves were used for vanillic acid (y = 8.1947x + 122.91; R² = 0.9976), chlorogenic acid (y = 85.138x + 135.16; R² = 0.9978), ferulic acid (y = 16.507x + 92.06; R² = 0.9980), quercetin (y = 112.8x + 287.12; R² = 0.9957), catechin (y = 41.108x + 335.6; R² = 0.9959) and rutin (y = 26.176x + 403.46; R² = 0.9924). The results are expressed as µg/g d.w.