Phytochemical analysis and antioxidant and anticancer activities of mastic gum resin from Pistacia atlantica subspecies kurdica

BACKGROUND: The mastic gum resin has been used in traditional Kurdish medicine for treating various disorders such as topical wound and gastric ulcer. The study designed to evaluate the total polyphenol and flavonoid content, free radical scavenging activity, and anticancer effects of mastic gum resin derived from Pistacia atlantica subspecies kurdica.

MATERIALS AND METHODS: Folin -Ciocalteau and the aluminum chloride colorimetric assays were used to determine the total phenol and flavonoid contents in the mastic gum resin respectively. Whereas, DPPH and ABTS+ assays were used to determine the antioxidant activities of mastic gum resin. Regarding anticancer activities, the MTT assay was used to study the effect of mastic gum resin on the proliferation of various cancer cells and the morphological changes were identified after Acridine Orange/Propidium Iodide staining. Flow cytometry was applied to determine the influence of mastic gum resin on the apoptosis rate by Annexin V double staining and to investigate the influence on cell cycle progression. Caspase colorimetric assay was used to estimate the hallmark enzyme of apoptosis, and finally RNA were obtained from COLO205 cells and analyzed by qRT-PCR analyses.

RESULTS: The MTT results showed that the mastic gum resin at concentrations from 0.01 to 100 μM induced death of cancer cells in a dose and time-dependent manner. The mastic gum resin suppressed proliferation of human cancer cells with 72 h IC50 value of 15.34 ± 0.21, 11.52 ± 0.18, 8.11 ± 0.23 and 5.2 ± 0.8 μg/mL for bile duct cancer (cholangiocarcinoma) (KMBC), pancreatic carcinoma (PANC-1), gastric adenocarcinoma (CRL-1739), and colonic adenocarcinoma (COLO205) cells, respectively. Normal human colon fibroblast (CCD-18Co) cells were not adversely affected by resin treatment. Flow cytometry showed that the mastic gum resin significantly (P<0.05) arrested COLO205 cell proliferation at the G2/M phase of cell cycle. The resin caused apoptotic morphological changes in COLO205 cells. The apoptotic effect to mastic gum resin was via the mitochondrial as shown by the up-regulation of Bax, down-regulation of Bcl-2 genes, and activation of caspase-9 and -3 activities.

CONCLUSION: It was confirmed that the antiproliferative efficacy of the resin is positively correlated with its polyphenolic contents, suggesting a causal link related to exudate content of phenolic acid and flavonoids. The results revealed that the mastic gum resin has potential to be developed as an anticancer and antioxidant product due to its high content of polyphenol compounds.