α-Pinene, an organic monoterpene, is found in essential oils of pine and coniferous trees. To date, although various biological activities of α-pinene have been demonstrated, its neurotoxicity has never been explored. Therefore in this study, we aimed to describe in vitro antiproliferative and/or cytotoxic properties by 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test, genotoxic damage potentials by single cell gel electrophoresis, and oxidative effects by total antioxidant capacity (TAC) and total oxidative stress (TOS) analysis of α-pinene. Statistical analysis of MTT assay results indicated significant (p < 0.05) decreases of the cell proliferation rates in healthy neurons treated with α-pinene at only 400 mg/L, while significant decreases were observed in N2a cells at 100, 200 and 400 mg/L. On the other hand, the mean values of the total scores of cells showing DNA damage were not found significantly different from the control values on both cells. In addition, our results indicated that 10 and 25 mg/L of α-pinene treatment caused increases of TAC levels in primary rat neurons without any alterations of its level in N2a cells. However, α-pinene treatments at higher doses led to increases of TOS levels in both cell types. Overall our results suggest that α-pinene is of a limited therapeutic use as an anticancer agent.

Terpinolene (TPO) is a natural monoterpene present in essential oils of many aromatic plant species. Although various biological activities of TPO have been demonstrated, its neurotoxicity has never been explored. In this in vitro study we investigated TPO's antiproliferative and/or cytotoxic properties using the 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) test, genotoxic damage potential using the single-cell gel electrophoresis (SCGE), and oxidative effects through total antioxidant capacity (TAC) and total oxidative stress (TOS) in cultured primary rat neurons and N2a neuroblastoma cells. Dose-dependent effects of TPO (at 10 mg L(-1), 25 mg L(-1), 50 mg L(-1), 100 mg L(-1), 200 mg L(-1), and 400 mg L(-1)) were tested in both cell types. Significant (P<0.05) decrease in cell proliferation were observed in cultured primary rat neurons starting with the dose of 100 mg L(-1) and in N2a neuroblastoma cells starting with 50 mg L(-1). TPO was not genotoxic in either cell type. In addition, TPO treatment at 10 mg L(-1), 25 mg L(-1), and 50 mg L(-1) increased TAC in primary rat neurons, but not in N2a cells. However, at concentrations above 50 mg L(-1) it increased TOS in both cell types. Our findings clearly demonstrate that TPO is a potent antiproliferative agent for brain tumour cells and may have potential as an anticancer agent, which needs to be further studied.

Carvacrol (CVC) is a phenolic monoterpene present in many essential oils of medicinal and aromatic plants and has attracted attention because of its beneficial biological activities. To date, although various biological activities of CVC have been demonstrated, its neurotoxicity on cultured primary rat neurons and N2a neuroblastoma cells has never been explored. Therefore, in this present study, we aimed to describe in vitro antiproliferative and/or cytotoxic properties (by 3-(4,5 dimetylthiazol -2-yl)-2,5 diphenlytetrazolium bromide (MTT) test), genotoxic damage potentials (by single cell gel electrophoresis (SCGE) or Comet assay) and antioxidant activities (by total antioxidant capacity (TAC) and total oxidative stress (TOS) analysis) of CVC in vitro. Dose (0-400 mg/L) dependent effects of CVC were tested on both cultured primary rat neurons and N2a neuroblastoma cells. Statistical analysis of MTT assay results indicated significant (p < 0.05) decreases of cell proliferation rates in both cell types treated with CVC at 200 and 400 mg/L. On the other hand, the mean values of the total scores of cells showing DNA damage (for comet assay) was not found significantly different from the control values for both cells (p > 0.05). In addition, our results indicated that 10, 25 and 50 mg/L of CVC treatment caused increases of TAC levels in cultured primary rat neurons but not in the N2a cell line. However, CVC treatments led to increases of TOS levels in cultured primary rat neurons at only 400 mg/L while they led to increases of TOS levels in N2a neuroblastoma cells at 200 and 400 mg/L. The present findings demonstrated that CVC could be a source of antioxidant and chemopreventive activities to be studied on cancer diseases.

α-Pinene (α-pinene), a bicyclic monoterpene, is present in the oils of many species of coniferous trees, most notably the pine, and is known for its diverse biological properties such as antimicrobial, anti-inflammatory, antiproliferative and antioxidant. However, there are limited data on the cytogenetic and antioxidant effects of α-pinene in cultured human blood cells (n = 5) for the first time. The purpose of this study was to investigate the genetic, oxidative, and cytotoxic effects of α-pinene in cultured human blood cells (n = 5) for the first time. Human blood cells were treated with α-pinene (0 to 200 mg/L) for 24 and 48 h, and then cytotoxicity was detected by lactate dehydrogenase (LDH) release and (3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide) (MTT) assay, while DNA damage was also analyzed by micronucleus (MN) assay, chromosomal aberration (CA) assay and 8-oxo-2-deoxyguanosine (8-OH-dG). In addition, biochemical parameters (total antioxidant capacity (TAC) and total oxidative stress (TOS)) were examined to determine oxidative effects. The results of LDH and MTT assays showed that α-pinene (at 200 mg/L) decreased cell viability. In our in vitro test systems, it was observed that α-pinene did not cause any statistically important changes in the rates of studied genotoxicity endpoints but dose-dependent alterations were observed in TAC and TOS levels. α-Pinene treatment caused increases in TAC levels (at 25 and 50 mg/L) and decreases in TOS levels (only at 200 mg/L) on human lymphocytes. In conclusion, the findings of the present study confirm for the first time that α-pinene could be a significant source of natural antioxidant compound that may have beneficial health effects.

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