Impact of Daily and Seasonal Variation on the Phytochemical Profile of Larrea cuneifolia in Northwestern Argentina

Abstract

Larrea cuneifolia Cav. (common name: jarilla macho), is an endemic Argentinianmedicinal shrub that has traditionally been used by the Diaguita-Calchaquí communities in theMonte Desert region in northwestern Argentina. The aim of the present study was to analyze thephytochemical profile and biological activity of the aerial parts of jarilla collected in different placesthroughout the whole year, in different seasons and times of day, to determine the optimalharvesting conditions for promoting its medicinal use. The aerial parts were collected three times aday over the course of four seasons in eight L. cuneifolia populations. The total phenoliccompounds (TPC), total flavonoid (TF) content, total lignans (TL), sugars (S) and soluble proteins(SP) content were quantified by using spectrophotometric methods and HPLC-DAD. Antioxidantactivity was determined by using ABTS scavenging. Significant seasonal, diurnal and spatialvariation in the accumulation of TPC (52.61 to 113.52 mg GAE/g), TF (3.71 to 17.92 mg QE/g), TL(283 to 582 g NDHGAE/g); S (5.73 to 15.17 mg GE/g) and SP (36.75 to 103.10 mg BSAE/g) inaerial parts of L. cuneifolia were revealed. The highest concentrations of TPC and TF wererecorded in spring mornings. Maximum accumulation of nordihydroguaiaretic acid (291.8 ± 2.8 gNDHGAE/mg dry weight) and other lignans were also observed in spring. Heat map analysespinpoint Ampimpa (Site 1) as a site for jarilla sustainable harvesting, balancing high metabolitecontent with population abundance, especially in spring, when the highest antioxidant activity(SC 50 = 1.560 ± 0.021 g GAE/mL) coincides with increased phenols levels. These studies highlight the importance of integrating ecological and phytochemical data to defining harvesting strategies; collecting during spring mornings optimizes the yield of bioactive compounds, simultaneously minimizing ecological pressure. This study demonstrates how seasonal bioprospecting can inform pharmacological research and local development while safeguarding the endemic plant population.