Biochemical responses and volatile compounds in a peppermint chemotype grown in a controlled environment

Abstract

Peppermint is a medicinal plant with great economic importance for its protective effects against biotic and abiotic factors. This study aimed to assess the vegetative growth, biochemistry and volatile production of peppermint plants under elicitation. Nodal segments were inoculated in flasks containing Murashige and Skoog medium with one of four treatments (50 µM salicylic acid, 200 mg L− 1 chitosan, 25 µM copper sulphate, and control) and maintained for 90 days in a controlled environment. Copper treatment increased shoot growth by 43% and 68% compared with salicylic acid and chitosan, respectively. Furthermore, copper elicitation reduced the oxidation rate to only 13% and produced plants with better architecture. Salicylic acid and chitosan treatments increased the total phenolic content by 38% and 40%, respectively, compared with the control. The ferric reducing assay showed that salicylic acid and chitosan treatments increased the plant’s antioxidant activity by 82% and 96%, respectively, compared with the control. However, β-carotene, flavonoids and anthocyanins decreased with these treatments. Phenylalanine ammonia-lyase activity increased by 63% and 54% in shoots elicited with salicylic acid and chitosan, respectively. Elicitor treatment increased the number of volatile compounds detected (control = 29, salicylic acid = 32, copper = 37, chitosan = 38). Elicitation promoted significant changes in plant metabolism and chemical composition, evidenced mainly by differences in the levels of 2-hydroxy-3-(3-methyl-2-butenyl)-3-cyclopenten-1-one, d-limonene, eucalyptol, caryophyllene and l-alanine ethylamide. Monoterpene hydrocarbons were the major class in control shoots, whereas oxygenated monoterpenes were the major compounds in elicited shoots.