Melissa officinalis extracts as potential acetylcholinesterase, tyrosinase and elastase enzymes inhibitors

Melissa officinalis L. (Lamiaceae family) has been employed since ancient times for both medicinal and alimentary purposes. Different preparations of this plant have been used in Traditional Medicine to treat several ailments, e.g. to treat anxiety, as memory enhancing, antiviral and antispasmodic, as wound healing 1,2,3. The aim of this work was to test different aqueous extracts obtained from M. officinalis for their potential activity against three different enzymes, acetylcholinesterase which modulates the cholinergic neurotransmission and tyrosinase and elastase involved in the hyperpigmentation and ageing of the skin, respectively. The extracts were first phytochemically characterized by high-performance liquid chromatography coupled to photodiode array and triple quadrupole mass spectrometer (HPLC-PDA-MS/MS), leading to the presence of polyphenols including cinnamic acid derivatives (e.g. caffeic and rosmarinic acids) and flavonoids (e.g. luteolin, quercetin and apigenin glucosides)2. Consequently, the potential inhibitory activities of the extracts towards the selected enzymes were evaluated through spectrophotometric tests. Results show that M. officinalis extracts are active as inhibitors of all the considered enzymes, with different rates of inhibition: about 10% for acetylcholinesterase (128 μg/ml), 14% for tyrosinase (3.3 μg/ml) and 40% for elastase (16.7 μg/ml). In addition to the samples, the pure standards of the main components found in the extracts were also tested (both alone and preparing mixtures of more compounds) to understand which were the most involved in the enzyme inhibition and the possible interactions among the considered compounds. The results allowed, in some cases, to better understand and explain the activity exerted by the extracts based on the activities showed by the tested compounds.