Antioxidant and Anticholinesterase Activities of Extracts and Phytochemicals of Syzygium antisepticum Leaves

Abstract

Bioassay-guided separation of young leaves extracts of Syzygium antisepticum (Blume) Merr. & L.M. Perry led to the isolation of four triterpenoids (betulinic acid, ursolic acid, jacoumaric acid, corosolic acid) and one sterol glucoside (daucosterol) from the ethyl acetate extract, and three polyphenols (gallic acid, myricitrin, and quercitrin) from the methanol (MeOH) extract. The MeOH extract of S. antisepticum and some isolated compounds, ursolic acid and gallic acid potentially exhibited acetylcholinesterase activity evaluated by Ellman's method. The MeOH extract and its isolated compounds, gallic acid, myricitrin, and quercitrin, also strongly elicited DPPH radical scavenging activity. In HEK-293 cells, the MeOH extract possessed cellular antioxidant effects by attenuating hydrogen peroxide (H₂O₂)-induced ROS production and increasing catalase, glutathione peroxidase-1 (GPx-1), and glutathione reductase (GRe). Furthermore, myricitrin and quercitrin also suppressed ROS production induced by H₂O₂ and induced GPx-1 and catalase production in HEK-293 cells. These results indicated that the young leaves of S. antisepticum are the potential sources of antioxidant and anticholinesterase agents. Consequently, S. antisepticum leaves are one of indigenous vegetables which advantage to promote the health and prevent diseases related to oxidative stress.

Keywords: Syzygium antisepticum; anticholinesterase; antioxidant; antioxidant enzyme; flavonoids; triterpenoids.

Figure 1

Isolated compounds from S. antisepticum young leaves.

Figure 2

Cytotoxicity profiles of the extract from S. antisepticum and flavonoid glycosides 7 and 8; HEK-293 cells were treated with methanol (MeOH) extract (0.5–500 μg/mL), myricitrin (7) (0.001–500 μM), or quercitrin (8) (0.001–500 μM) for 36 h. Data are shown as the percentage of cell viability (mean ± SEM) (n = 4).

Figure 3

Cellular antioxidant effects of the methanol (MeOH) extract and flavonoid glycosides 7 and 8 from S. antisepticum; HEK-293 cells were treated with either methanol extract (50 and 100 μg/mL), myricitrin (7) (10 μM), quercitrin (8) (10 μM), or vitamin C (10 μM) for 3 h and then treated with H₂O₂ (100 μM) for 1 h. Data are shown as the percentage of ROS levels (mean ± SEM) as compared with that in control (vehicle; DMSO) group (n = 4). * p < 0.05 versus control; ^# p < 0.05 versus the H₂O₂ group.

Figure 4

Effects of the methanol extract and flavonoid glycosides 7 and 8 from S. antisepticum on upregulation of antioxidant mRNA levels; HEK-293 cells were treated with either methanol extract of S. antisepticum (100 μg/mL), myricitrin (7) (10 μM), or quercitrin (8) (10 μM) for 6 h. The relative mRNA expression levels were quantified and shown as mean ± SEM as fold over basal (vehicle, DMSO) (n = 4). * p < 0.05 versus control.