Syringic acid

Syringic acid ameliorates the expressions of TH, DAT and VMAT2 and also significantly attenuates MPTP/p2 induced increased inflammatory markers expression^[1]. SYRA pretreatment obviously inhibits H2O2-induced RGC-5 cell injury and also decreases H2O2-induced ROS production and MDA content. Syringic acid may protect RGC-5 cells against apoptosis induced by H2O2 through the activation of PI3K/Akt signaling pathway^[3]. Syringic acid shows a time- and dose-dependent (IC50 = 0.95-1.2 mg/mL) antimitogenic effect against cancer cells with little cytotoxicity on normal fibroblasts (≤20%). SYRA alters cell cycle (S/G2-M or G1/G2-M phases) in a time-dependent manner, induces apoptosis, inhibits DNA-binding activity of NFκB (p ≤ 0.0001), chymotrypsin-like/PGPH (peptidyl-glutamyl peptide-hydrolyzing) (p ≤ 0.0001) and the trypsin-like (p ≤ 0.002) activities of 26S proteasome and angiogenesis. SYRA also differentially sensitizes cancer cells to standard chemotherapies with a marked increase in their sensitivity to camptothecin (500-fold), 5FU (20,000-fold), doxorubicin (210-fold), taxol (3134-fold), vinblastine (1000-fold), vincristine (130-fold) and amsacrine (107-fold) compared to standard drugs alone. SYRA exerts its chemotherapeutic and chemo-sensitizing effects through an array of mechanisms including cell-cycle arrest, apoptosis induction, inhibition of cell proliferation, cell migration, angiogenesis, NFκB DNA-binding and proteasome activities^[4].

Colorectal cancer cell lines(SW1116 and SW837) and normal human fibroblasts (CRL1554) are plated in 96-well microtiter plates at a cell density of 27×10³ cells/well. Cells are incubated for 24-72 h in a culture medium containing increasing concentration of SA (0-2 mg/mL)at 37℃ in a non-CO2 incubator. After completion of the treatment period, the media are discarded and 100 mL/well of MTT (5 mg/mL membrane filter sterilized culture medium) is added and the plate is incubated for 4 h at 37℃. MTT solution is aspirated and the purple-colored formazan crystals, thus formed, are dissolved in 200mL/well of DMSO:ethanol (1:1; v/v) for 20 min at ambient temperature to lyse the cells and dissolve the colored crystals formed in viable cells.

Syringic acid has hepatoprotective effects in various animal models. Oral administration of SYRA (10mg/kg of body weight) is reported partial recovery of learning and memory impairment by amyloid β induced neurotoxicity in mice. SYRA also facilitates protective effects on kidney in renal ischemia-reperfusion injury. Antimicrobial activities of SYRA are also reported against various pathogens. Anticancer effects of SYRA are explored on A549 lung carcinoma cells and is found to show apoptotic effects with an IC50 of 30 μM^[1]. Syringic acid attenuates the elevation of glycoprotein components in normal and diabetic rats. Syringic acid may increase insulin secretion of pancreatic β-cells and normalize the plasma glucose level^[2].