Comparison monoterpene and sesquiterpene, herbage yield of Satureja hortensis, Thymus vulgaris, and Salvia officinalis from the Fars province of Iran

Abstract Recently, numerous side effects of synthetic drugs have led to using medicinal plants as a reliable source of new therapy. Pain is a global public health problem with a high impact on life quality and a huge economic implication, becoming one of the most important enemies in modern medicine. The medicinal use of plants as analgesic or antinociceptive drugs in traditional therapy is estimated to be about 80% of the world population. The lamiaceae family, one of the most important herbal families, incorporates a wide variety of plants with biological and medical applications. In this study, the main active compounds of Thymus vulgaris (thymol (51.59%), p-cymene (15.41%), carvacrol (4.52%) and γ-terpinene (12.63%), Salvia officinalis; cis-thujone (38.05%), camphor (16.08%), 1,8-cineole (11.97%), trans-thujone (5.88%), camphene (4.79%), α -pinene (4.69%) and carvacrol (50.68%), γ-terpinene (34.44%) and α-terpinene (3.72%) in Satureja hortensis was determined. The highest EO contents (w/w %) was obtained in the plants of summer savory (2.05%), followed by the garden thyme (1.83%) and common sage (0.55%). It is necessary to identify the most effective compounds in order to extract or synthesise in pure form for future use in the pharmaceutical industry. Also, might be used for isolation of potentially active compounds from some of these medicinal plants in future and formulation of commercial therapeutic agents. Graphical Abstract


Introduction
As sessile creatures, plants have to adapt themselves in response to a variety of environmental signals.Despite the fact that secondary metabolites play an important role in the plants' adaptability, natural phytochemical variations and subsequently different bioactivities are inevitable to occur among different populations located in various regions (Labarrere et al. 2019).The majority of Iranian native medicinal plants have a wide geographical distribution and grow spontaneously in a range of bioclimatic zones (Fattahi et al. 2016).One of the challenges in studying chemical diversity is identifying the variables that cause chemical polymorphism in plant populations, which is typically connected to environmental and genetic factors.To have a better knowledge of the variables that affect the plant secondary metabolites diversity, characterisation of the phytochemicals diversity from native populations in various locations is required (Mart ınez-Natar en et al. 2012).
On the other hand, the use of various plant species as flavoring herbs and preserving the germplasm for the purpose of improving the nutritional properties and medicine compounds has been widely practiced among different nations since the ancient times.Natural essential oils of medicinal plants have recently gained scientific attention to meet the requirements of health and safety in food and medicine industries (Geng et al. 2016).
Lamiaceae family is the most diverse and extensive herbal family in the field of Pharmaceutical studies and their Pharmaceutical importance is due to the essential oil available in them (Sharafzadeh et al. 2011).Thymes species are regarded as important medicinal plants which have extensive medical use due to the high yield of their essential oil and valuable secondary metabolites, especially thymol and carvacrol (Askary et al. 2018).Summer savory (Satureja hortensis L.) as an endemic species identified in Iran and other countries is widely used in traditional medicine.Several isolated molecules of this species are used to elaborate antifungals and can also be used in the pharmaceutical industry (Fathi et al. 2011).The raw material of this species was applied for the preservation of food (Semerdjieva et al. 2020) and production of plant-derived drugs (Mozafari et al. 2018) .Sage (Salvia officinalis L.) as the main herb in the world is cultivated in many countries.Essential oil from the sage leaf is used as raw material in pharmaceutical and cosmetics industries (Rahmani et al. 2019).
On the other hand, the use of cultivars with distinguished and improved properties is the prerequisite for the industrial production (Herison 2018).Different environmental conditions in which each population habited could be a logical reason for the observed inter-population EO variations.Each population, as a rich source of phytochemical compounds and natural antioxidants, with a unique capacity to produce EO and phenolic compounds, could be considered as an option in a selection process of endemic plant domestication and further breeding program and industrialisation (Narimani et al. 2021).thus, the present study is conducted to investigate the chemical composition of EOs from: summer savory (Satureja hortensis), garden thyme) Thymus vulgaris (, common sage) Salvia officinalis) cultivated in Iran.Furthermore, these findings may benefit essential oil producers and consumers, who utilise these compounds in pharmaceutical and cosmetic industries.

Chemical composition of the essential oils
The content of essential oil in the air-dry mass of the above-ground parts of plants of three plants was from 0.55% to 2.05% in the stage of mass flowering.Respectively, in sage the yield was 0.55% lower, and in thyme by 1.83% lower than that of savory (Figure S1).
The results found in this study are in line with the valuable results of other researchers in various plants.
Thymes can be regarded as a member of this family which is of great importance in Iran and other parts of the world, and is highly notable due to its high essential oil yield and valuable phenolic compounds, specially thymol and carvacrol (Safaei-Ghomi et al. 2009).The essential oil of thymes is known as thyme including phenols such as thymol, carvacrol, p-cymene and c-Terpinene.Generally, thymol and carvacrol are the most important compound available in the thymes essential oil which have biological activity (Askary et al. 2018).
In this study, the most monoterpene carvacrol and c-terpinene were found in S. hortensis.Carvacrol possesses a wide range of bioactivities putatively useful for clinical applications such antimicrobial, antioxidant, and anticancer activities.Carvacrol antimicrobial activity is higher than that of other volatile compounds present in essential oils due to the presence of the free hydroxyl group, hydrophobicity, and the phenol moiety (Sharifi-Rad et al. 2018).
On the other hand, the highest monoterpene thymol (51.59%), p-cymene (15.41%) was found in thyme.Thymol is a natural volatile monoterpenoid phenol that is the main active ingredient of oil extracted from species Thymus vulgaris commonly known as thyme.Its pharmacological applications have been the most investigated and reported, focusing on its prominent antimicrobial, antioxidant, anti-inflammatory, cicatrising activities.Furthermore, it is noteworthy that the research on its agricultural applications has increased, highlighting its uses as a natural agrochemical and preservative to safeguard foods from pathogenic microorganisms both in sowing and storage, which could have a beneficial effect on human health and the environment.Research has also been reported on its activity as an insecticide, acaricide, and animal repellent.(Escobar et al. 2020).
Finally, most cis thujone (38.05%), camphor (16.08%), 1,8-cineole (11.97%) were found in sage.Camphor is applied to the skin to increase local blood flow and as a 'counterirritant', which reduces pain and swelling by causing irritation.Some people apply camphor to the skin to treat diseases of the airway and to treat heart symptoms.Camphor is also applied as an eardrop and for treating minor burns.Also, Thujone is an ingredient of essential oils of different herbs and causes exciting effects in the central nervous system (Bielenberg 2007).

Conclusions
The obtained results indicated that it is necessary to identify the most effective compounds in order to extract or synthesise in pure form for future use in the pharmaceutical industry.It is also imperative that essential oils should be further examined, so that safe conclusions can be drawn about their potential use, Moreover, these EOs can substitute for many common synthetic drugs.Also, might be used for isolation of potentially active compounds from some of these medicinal plants in future and formulation of commercial therapeutic agents.

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
The author(s) reported there is no funding associated with the work featured in this article.