Evaluation of essential oil composition and antioxidant activity of yarrow as influenced by foliar application of humic substance-based products: Using multivariate exploratory method

Abstract

The growth-promoting ability with the organic fertilizers especially humic substance-based products, it has caused their use to be considered. This research aimed to investigate the effect of foliar application of humic and fulvic acids on essential oil compositions and antioxidant activity of yarrow (Achillea millefolium L.) based on Principal Component Analysis (PCA) and calculating the selection criterion (SC) to identify the main chemical compositions. Treatments consisted of four applied levels of humic acid, HA (Control: 0, HA1: 250, HA2: 500, and HA3: 1000 mg L−1) and fulvic acid, FA (Control: 0, FA1: 250, FA2: 500, and FA3: 1000 mg L−1). According to the results, two PCs had eigenvalues ≥ 1 and showed 80.75% and 65.84% of variance with application of HA and FA, respectively. Based on the results, HA and FA had significant effects on the amount of important medicinal compounds. The main essential oil compounds of different HA- and FA-treated plants were: α-pinene (0.81–6.44%), 1-octen-3-ol (2.68–16.55%), p-cymene (2.85–6.90%), 1,8-cineole (0.45–4.06%), camphor (0.36–6.90%), borneol (3.91–22.83%), myrtenol (2.02–2.88%), thymol (1.01–2.59%), E- caryophyllene (0.39–1.98%), spathulenol (2.3–19.3%), and caryophyllene oxide (5.93–12.60%). According to the calculated coefficient of determination (R2), the maximum positive effects of FA addition were observed for E- caryophyllene, α-terpineol, terpinen-4-ol, and benzaldehyde (R2 = 0.98, 0.93, 0.91, and 0.84, respectively), and that of HA application were obtained for cis-cadin-4-en-7-ol and spathulenol (R2 = 0.99 and 0.92). Results showed that the antioxidant activity of yarrow plant extract significantly improved when FA especially at high levels (i.e., 500 and 1000 mg L−1) was applied. On the other hand, in HA-treated plants, only application of 1000 mg L−1 had a positive effect. Findings of the present study can be used to manage production of medicinal plants and the quality of their products. In addition, in sustainable agriculture, using humic substances can reduce the application rate of chemical fertilizers, thereby maintaining the environment.