Effect of arbuscular mycorrhizal fungi on the essential oil composition and antioxidant activity of black pepper (Piper nigrum L.)

Summary. Piper nigrum plants were inoculated by spores of arbuscular mycorrhizal fungi (AMF) and after 120 days, the essential oils (EO) and extracts of leaves and roots were obtained. The AMF inoculation promoted a decrease of sesquiterpene hydrocarbons (25.4% to 10.6%) and an increase of oxygenated sesquiterpenes (67.0% to 82.7%) in the leaf EO. In addition, an increase of the main compounds α-bisabolol (32.3% to 48.5%) and elemol (11.4% to 23.2%) was observed. However, in the roots EO the main compounds were monoterpenes as camphene, sabinene and limonene, which did not display variation. The leaf extract showed a significant variation in total phenolic content (6.8 ± 0.2 to 16.4 ± 1.0 mg AGE/g) and antioxidant activity (12.3 ± 2.0 to 73.7 ± 1.4 mg TE/g). The oils and extracts of the roots remained almost unchanged, suggesting that the inoculation with AMF induces a systemic response in P. nigrum and affects mainly the leaves. Industrial relevance. Piper nigrum essential oil is used as flavoring, antimicrobial and antioxidant agent in food preservation. These proprieties are attributed to the presence of the oxygenated sesquiterpenoids α-bisabolol and elemol, which displayed an increased its content after AMF inoculation. Keywords. Black pepper; AMF colonization; α-bisabolol; phenolic compounds; antioxidant activity