In vitro biocompatibility and oral anti-bacterial activity of the Sardinian plants Citrus lemon var pompia and Thymus herba-barona

Aim: To assess the biocompatibility and anti-bacterial activity of phytocomplex of Citrus lemon var. pompia (CLP) and essential oil of Thyme herba-barona Loisel (THB) in innovative phospholipid vesicles. Methods: CLP was obtained by the rind of fresh fruits using an ethanol/water mixture. THB was obtained by the aerial part of the plant by hydrodistillation. They were loaded into phospholipid vesicles prepared with 60 mg/ml of soy phosphatidylcholine in water/propylene glycol 1/1 (PG-liposomes) or water/glycerol 1/1 (glycerosomes). The size and zeta potential were misused using a Zetasizer Nano. The potential safety of the agents was assessed using human primary gingival fibroblasts (HGF) for 48 h of exposure using the MTT colorimetric assay, added to 200 µl of MTT reagent to each well. Results were calculated in term of cell viability in comparison to non-treated controls. Anti-bacterial activity was carried out using the bacterial inhibition halo test using a 0,5 Mc Farland suspension of planktonic Streptococcus mutans (ATCC 35668), Lactobacillus acidophilus (ATTC 4356) and Candida albicans (ATTC 10231) in contact to 0,15 um of each cell for 24 hours at 37°. Results: The vesicles dispersion appeared yellow-transparent, homogeneous and stabile. The vesicles were spherical, unilamellar, small in size and negatively charged. The size of liposomes ranged to 90-140 um and the addition of phospholipid vesicles caused a slight size reduction. None of the agents expressed cytotoxicity in term of proliferation inhibition or viability reduction of the HGF in comparison to the controls. The inhibition halo test demonstrated the efficiency of the agents against Streptococcus mutans and Lactobacillus acidophilus independently by the addition to phospholipid vesicles. Moreover, THB in the different formulations was able to inhibit Candida albicans. Conclusions: The biocompatibility and anti-bacterial activity of CLP and THB suggest a possible use as natural antimicrobial agents in the oral cavity.