Evaluation of Myrtus communis L. as a phytotherapeutic with neuroprotective effect

In the current thesis study, the leaf samples of the plant samples belonging to the cultivated white fruit (Hambeles) and black fruit (Yakup) cultivars of Myrtus communis L. from the Myrtaceae family were collected during 12 months and the mature fruit samples were also taken. The ethanol extracts were prepared from the leaf and fruit samples and tested by ELISA method for their in vitro inhibitory activity against cholinesterase enzyme family consisting of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) as well as tyrosinase (TYR). In order to determine the phenolic compounds of the leaf extracts of Hambeles and Yakup varieties and the fruit extracts of these two varieties, which are known to be rich in polyphenols, collected during 12 months, phytochemical analyzes were performed on a total of 26 extracts using liquid chromatography-mass spectrophotometer (LC-MS) technique. Total phenol and flavonoid amounts were determined in the extracts, while the phenolic compounds, e.g. galloyl glucose isomers 1 and 2, quinic acid isomer, galloyl quinic acid isomers 1, 2 and 3, strictin isomers 1 and 2, digalloyl quinic acid isomer, digalloyl-hexahydroxyphenol-glucose isomers 1 and 2, trigalloyl glucose, myricetin galloyl hexoside, myricetin galactoside, myricetin galloyl rhamnopyranoside, myricetin-3-O-arabinoside, myricetin-3-O-rhamnoside, kaempferol-O-galloyl-hexoside, and quercetin rhamnoside were determined to exist commonly in the extracts by LC-Q-ToF-MS. IC50 value of the leaf extract of the Hambeles variety from January collection, which caused the highest cholinesterase inhibition, was calculated as 18.49 ± 3.50 g/mL. IC50 values of galanthamine used as reference against AChE and BChE were 1.33 ± 0.11 and 37.69 ± 2.93µg/mL, respectively. The extracts caused low inhibition against TRY, ranging from 7.14 ± 3.03 to 17.32 ± 1.98 µg/mL. In addition, in our cholinesterase enzyme inhibitory activity experiments, the effect of the leaf extract of Hambeles variety from January collection, which showed the highest cholinesterase inhibition, against the neurotoxicity induced by 6-OHDA in SHSY-5Y cells was investigated. According to this; consistent with cell viability analyzes, the highest cytotoxic value was observed at 100 µg/mL concentration of the extract applied for 24 hours after pre-application of 100 µM 6-OHDA for 24 hours. This study constitutes the first study on M. communis leaf and fruit extracts cultivated in our country regarding annual changes in the phytochemistry relevant to its phenolic components as well as neuroprotective effect through cholinesterase and TYR enzyme inhibition along with cell culture assays.