Polygonum odoratum essential oil inhibits the activity of mushroom derived tyrosinase

Plant derived compounds are a source of long term research focus due to their applications in a variety of fields, particularly food preservation. One key way in which phytochemicals are crucial in this area is by disrupting enzyme functionality. In this work, essential oil was extracted by steam distillation from the fresh leaves of Polygonum odoratum (Polygonaceae), commonly known as Vietnamese coriander, and shown to effectively inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase (EC1.14.18.1). Using GC-MS analysis, twenty five compounds were identified in the essential oil. The most abundant compounds in the essential oil were Alkanals - dodecanal (55.49%), and decanal (11.57%) - followed by anisaldehyde (6.35%); these compounds were individually investigated for inhibitory activity by performing single-compound screening. Each of the top three most abundant compounds inhibited the tyrosinase-catalyzed oxidation of L-DOPA, as identified by UV-VIS spectroscopy and oxygen consumption assays. The inhibitory activity of the major compounds increased when pre-incubated with tyrosinase and without significant additional oxygen consumption, suggesting k(cat)-type inactivation is not involved. Interactions of the head and tail components of the major alkanals may disrupt the tertiary structure of the enzyme, presenting a potential inhibitory mechanism.