Chemical composition and biological evaluation of the resin from Tetraclinis articulata (Vahl.) Masters: A promising source of bioactive secondary metabolites

The identification of the volatile components of the resin from Tetraclinis articulata (Vahl.) Masters and its non-polar fractions 1–5 obtained by chromatographic simplification was investigated by GC-FID and GC–MS and allowed the identification of 97.3% (resin), 95.1% (1), 97.6% (2), 99.6% (3), 88.1% (4) and 95.0% (5) of the total volatile components. The resin and its fractions were characterized by the presence of a high amount of diterpenes (87.4, 80.1, 91.0, 91.6, 65.7 and 69.1%, respectively). The major identified diterpenes were trans-ferruginol (resin: 31.6%, 1: 56.5% and 2: 48.0%), manool (3: 57.0% and 4: 42.0%) and trans-totarol (5: 36.2%). In addition, trans-communic acid was isolated together with its cis diastereoisomer from the fraction 6 of the resin and identified by spectroscopic means (1D and 2D NMR) and by comparison with literature data. The resin, its fractions 1–5, trans-communic acid and cis-trans mixture were screened for their antioxidant activity using DPPH, ABTS, reducing power, catalase and paraoxonase methods, as well as for their antibacterial, anticholinesterase, anti-tyrosinase and cytotoxic potentials. The fraction 2 displayed the highest antioxidant activity (IC50= 25 ± 1 μg/mL and 64.1 ± 0.5 μM/min/L) in DPPH and paraoxonase assays, respectively. Trans-communic acid was found to be antibacterial against Staphylococus aureus and Enterococcus faecalis (IZ = 23.9 ± 1.5 and 20.5 ± 0.5 mm, respectively). Furthermore, the resin showed the best anti-tyrosinase activity with 87.2% of inhibition at 50 μg/mL and cis-trans mixture exerted a significant cytotoxic effect against HeLa cell line (IC50= 09.5 ± 1.0 μg/mL).