Optimizing the Distillation of Greek Oregano-Do Process Parameters Affect Bioactive Aroma Constituents and In Vitro Antioxidant Activity?

Alexandros Nakas; Georgia Giannarelli; Ioannis Fotopoulos; Eirini Chainoglou; Aikaterini Peperidou; Konstantinos N Kontogiannopoulos; Artemis Tsiaprazi-Stamou; Vasilios Varsamis; Helen Gika; Dimitra Hadjipavlou-Litina; Andreana N Assimopoulou

doi:10.3390/molecules28030971

Optimizing the Distillation of Greek Oregano-Do Process Parameters Affect Bioactive Aroma Constituents and In Vitro Antioxidant Activity?

Molecules. 2023 Jan 18;28(3):971. doi: 10.3390/molecules28030971.

Authors

Affiliations

¹ Laboratory of Organic Chemistry, School of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
² Natural Products Research Centre of Excellence, Center for Interdisciplinary Research and Innovation of Aristotle University of Thessaloniki, 57001 Thessaloniki, Greece.
³ Department of Pharmaceutical Chemistry, Faculty of Health Sciences, School of Pharmacy, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.
⁴ Vessel Essential Oils, Neo Rysio, 57001 Thessaloniki, Greece.
⁵ School of Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece.

Abstract

The aim of the present work was to optimize the conditions of the distillation process at a pilot scale to maximize the yield of specific bioactive compounds of the essential oil of oregano cultivated in Greece, and subsequently to study the in vitro antioxidant activity of these oils. Steam distillation was conducted at an industrial distillery and a Face-Centered Composite (FCC) experimental design was applied by utilizing three distillation factors: time, steam pressure and temperature. Essential oil composition was determined by static headspace gas chromatography-mass spectrometry (HS-GC/MS). To obtain a comprehensive profile of the essential oils, instrumental parameters were optimized, including sample preparation, incubation conditions, sampling process, injection parameters, column thermal gradient and MS conditions. With the applied GC-MS method, more than 20 volatile compounds were identified in the headspace of the oregano essential oils and their relative percentages were recorded. Carvacrol was the most prominent constituent under all distillation conditions applied. Data processing revealed time as the main factor which most affected the yield. The Desired Space (DSc) was determined by conducting a three-dimensional response surface analysis of the independent and dependent variables, choosing yields of thymol and carvacrol as optimization criteria. The in vitro antioxidant activity of the essential oils of all samples was measured in terms of the interaction with the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) after 20 and 60 min. The most prominent essential oils at different distillation conditions were also tested as inhibitors of lipid peroxidation. Higher % values of carvacrol and thymol were correlated to higher antioxidant activity. Evaluating the impact of the distillation conditions on the in vitro results, it seems that lower pressure, less time and higher temperature are crucial for enhanced antioxidant activities.

Keywords: antioxidant activity; design of experiments; essential oils; headspace GC-MS; oregano.

MeSH terms

Antioxidants / chemistry
Greece
Odorants / analysis
Oils, Volatile* / chemistry
Oils, Volatile* / pharmacology
Origanum* / chemistry
Steam
Thymol / analysis

Substances

Antioxidants
carvacrol
Thymol
Steam
Oils, Volatile

Grants and funding

T1EDK-04174, AROMADISTIL/European Union and Greek national funds (Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH - CREATE - INNOVATE)