Absorption and Bioavailability of Major Monoterpenes in Mastiha Oil; a Kinetic Study in Humans.

Plant derived foods contain large quantities of non-nutrient phytochemicals that have been extensively studied for their beneficial health effects on the prevention of chronic diseases. Although research on their health effects is abundant, our knowledge on absorption and bioavailability is yet narrow and in some cases zero. The concept of bioavailability involves the identification of the fraction of administered compounds that can reach plasma and body tissues in an unchanged form. The bioactivity of components in foods that are part of our nutrition, either as parent foods or as food supplements, is directly related to bioavailability, the latter being a necessary step to prove efficacy.

Mastiha Oil (MO) is extracted from the resin of Pistacia Lentiscus var. Chia (of the Anacardiaceae family), a concentrated source of monoterpenes (e.g., α-pinene, β-pinene, β-myrcene) and triterpenes (e.g., mastihadienonic acid, isomastihadienonic acid), and to a lesser extent of plant sterols, simple phenols and approximately 10% MO (Assimopoulou, \& Papageorgiou, 2005, Paraschos et al, 2007, Kaliora, Mylona, Chiou, Petsios, \& Andrikopoulos, 2004). MO is a 100% natural product used as a food additive and flavoring and it is manufactured according to the legal standards that make it suitable for human consumption. Its nutritional analysis is presented in Supplementary Table 1. A total of 90 components have been detected in MO (50% monoterpene hydrocarbons, 20% oxygenated monoterpenes, 25% sesquiterpenes). Monoterpenes seem to exhibit beneficial health effects contributing to mechanisms of inflammation and oxidative stress (Subramaniyan, 2017; Madhuri, \& Naik, 2017).

Research upon the bioavailability of monoterpenes in humans is limited. Herein, we aimed at investigating the bioavailability of the main monoterpenes of MO in humans for the first time. To this end, a novel GC-MS-MS method was employed, since the tandem MS technique can help overcome matrix difficulties. Additionally, based on the existing data regarding the antioxidant activity of monoterpenes, the effect on human antioxidant capacity was evaluated applying the serum oxidisabilty assay.

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After enrolment, the volunteers will undergo a medical and dietary assessment and their health status will be evaluated through a complete blood count. On the day of the experiment and after overnight fasting, the volunteers will consume g of mastiha oil (1ml) and blood samples will be obtained on timepoints 0.5h, 1h, 2h, 4h, 6h and 24h after intake. Until timepoint 6h, they will be allowed to consume only water. After collection, the monoterpenes will be identified in plasma samples applying a GC-MS-MS technique. Additionally, oxidative stress will be evaluated through the CuSO4 technique in serum samples.

Eligibility Criteria:
Inclusion Criteria:

* Age: 20-40 years old
* BMI: 18.5-24.9 kg/m2

Exclusion Criteria:

* Obesity
* Alcohol or drug abuse
* Medication, vitamin or inorganic supplements
* Vegan or macrobiotic diet before and during the study
* Gastrointestinal diseases, such as atrophic gastritis, Inflammatory Bowel Disease, peptic ulcer or gastrointestinal cancer