Identification of Diurnal Variation of Essential Oil Components of Hypericum perfoliatumL .(Hypericaceae)

In this study, the diurnal variability of essential oil components of the species Hypericum perfoliatum was investigated. To determine diurnal variation, during the flowering period collection was carried out at three different times of the day (9a.m., 12a.m., 4p.m.). As a result of this research, it was aimed to determine the most appropriate harvest time during the day. The essential oil components were analyzed using GC-MS device after the production of essential oil was determined by hydrodystylation method. The main components of essential oils were found to contain mainly α-pinene (41.2%), β-pinene (6.2%), n-nonane (5.6%), ϒ-muurolene (4.7%), α-calacorene (4.2%), δ-cadinene (3.7%), n-undecane (3.2%) and caryophyllene oxide (3.1%).


Introduction
Turkey is an important gene center in terms of Hypericum L. (Hypericaceae) species. Hypericum genus, which is represented by approximately 500 species in the world, is represented by more than 100 taxa in Turkey, 44 of these taxa which are endemic [1]. Hypericum species have been used in the treatment of certain diseases in public medicine since the earliest times of history. In particular, Hypericum perforatum is successfully used by many countries to treat stomach ailments skin wounds, and especially antidepressants [2]. Due to these proven medicinal effects, it is a plant in most pharmacopoeia and monographs [3].
The development of these plants has reduced the use of all synthetic pharmaceutical industry, although synthetic drugs and herbal medicines to have effect dangerous side effects of a multifaceted, active compounds have stimulated studies on these plants and those obtained. However, the fact that it is difficult to collect from nature and the fact that the existence of its species is endangered makes it necessary to take these plants into culture [4].

MCDA.000676. 8(1).2021
During the period of full flowering plants at three different times of the day (9a.m., 12a.m. and 4p.m.) biodiversity and plant samples were taken and placed in polyethylene bags, without damaging the surface from the distribution area on labeled. The collected plant material was dried in the shade at room temperature (21 °C).

GC-MS analysis
The determination of essential oil components of the samples was made by Thermo Electron Trace 2000 GC Model gas chromatography and Thermo Electron DSQ Quadrupole mass spectrometer in TÜBITAK Ume Chemistry Laboratory. A homologous n-alkane series has been used as a reference in the calculation of Kovats indices (KI) ( Table 1). The identification of the compounds was based on comparison of retention times and mass spectra with those obtained from the NIST and Wiley spectra from the original samples and from literature data [10].
In the fat Rose (Rosa damascena Mill.) in their study on determination of ontogenetic, morphogenetic and diurnal variability, they found that the ratio of essential oil decreased rapidly from morning hours to evening hours and the main component rates decreased [11]. In their study on the effect of diurnal variability on yield and quality in Thymbra capitata genotypes, found that the most appropriate collection time in terms of essential oil ratio and components was in the morning hours [12]. They determined the most suitable collection time as noon in the species Hypericum montbretii Spach [13].
Differences in research results are that the chemical composition of essential oil varies according to climatic, seasonal and geographical conditions [15].

Conclusion
In this study, the diurnal variability of the essential oil components of the H. perfoliatum species was determined. The highest amount of essential oil in H. perfoliatum was obtained from plants collected in the morning. The main components of essential oil were determined as α-Pinene, β-Pinene and n-Nonane, and it was determined that it reached the highest values in plants collected in the morning (8a.m.).
In this study, the most appropriate collection time for the essential oil components of the species examined was determined and the most effective utilization method was determined. In addition, we believe that this study will contribute to obtaining effective results in various scientific studies, especially phytochemical and pharmaceuticals, for the collection of other Hypericum taxa to be used other than H. perfoliatum.