3.2. Essential oils
The aerial parts of H. heterophyllum were recorded to contain 0.09±0.01%, 0.087±0.006%, 0.05±0.00% and 0.077±0.02% essential oil for BF1, BF2, 50%F, and FF stages, respectively (Figure 4). Essential oil contents recorded in the BF1, BF2 and FF stages did not show statistically (p ≤0.05) significant differences. However, the highest and lowest essential oil content was obtained from BF1 and 50%F stage, respectively. In the previous study, it was stated that hydrodistillation of the dried aerial parts of H. heterophyllumyielded 0.09% of the essential oil (Cakir et al., 2004). The amount of the essential oil from aerial parts of H. aucheri , H. montbretii , H. kazdaghensis , and H. perforatum was 0.28%, 0.22%, 0.17% and 0.23% in the before flowering, 0.27%, 0.20%, 0.24% and 0.33% in the beginning of flowering, 0.33%, 0.23%,0.26% and 0.37% in the full flowering, 0.02%, 0.03%, 0.02%, and 0.05% in the capsule during, respectively (Pasa, 2013). In the fourHypericum species, the highest essential oil ratio was obtained from the plants harvested in full flowering period. In our study, the highest rate of essential oil was recorded in BF2, followed by FF.
The chemical components of H. heterophyllum essential oils from four different development stages was given in Table 6 The total of 15, 15, 13, and 16 components representing 92.19%, 80.08%, 90.13%, and 84.24% of the total essential oils were detected in the BF1, BF2, 50%F, and FF stages, respectively.
In this study, germacrene-D, bicyclogermacrene, δ-cadinene, spathulenol, α-guaiene, and valencene having significant biological activities were found to be main components of essential oils obtained from different ontogenetic stages of H. heterophyllum (Table 6 and Table 8). In the study carried out by Cakir et al (2004), in the essential oil ofH. heterophyllum , 35 compounds, representing 99.4% of the total essential oil, were determined, and isocaryophyllene (17.1%), α-pinene (11.6%), δ-cadinene (9.5%), γ-muurolene (8.2%), γ-cadinene (5.5%), n-decane (5.8%), and β-Caryophyllene (4.5%) were recorded as major compounds in this essential oil. Although there is similarity between these findings and present study, there are some differences. Essential oil components have been reported to be affected by many intrinsic (genetic, plant origin, type of plant part, stage of development or seasonal sampling period etc.) and extrinsic factors (environmental factors such as climate and habitat conditions, sowing date, cultivation conditions, and postharvest techniques such as drying methods and extractions, distillation time, and conditions of analysis) (Moghaddam & Mehdizadeh, 2017).
The variation of the main components has been given in Figure 5. The highest concentrations of germacrene-D were recorded in the BF1, 50%F, and BF2 stages, respectively. This component showed a significant decrease by average 3 times in the FF stage. Bicyclogermacrene reached the maximum concentration in the BF1 stage. The amount of this compound reduced approximately to half in the 50%F and BF2 stages, and it was not detected in the FF stage. Although the highest amount of δ-cadinene was recorded in the FF period, similar rates were obtained in BF1 and 50%F stages. But a decrease of about 7% was observed in the BF2 stage. The highest ratio of spathulenol was recorded in the 50%F stage, followed by the BF2 stage. The lowest ratio was obtained from BF1 stage. The amount of valencene being among the minor components in the BF1, BF2 and 50%F stages was found to be 9.76 % in the FF stage. α-Guaiene was detected only in the essential oil in the FF stage (Table 6). Significant differences in the concentrations of the main components ofH. heterophyllum essential oil were determined according to the developmental stages. A similar situation was observed in the minor components of the essential oil such as β-caryophyllene, α-humulene, aromadendrene, viridiflorol, globulol, salvial-4(14)-en-1-one, isospathulenol, tau-muurolol, α-amorphene, and α-cadinol (Table 6).
In terms of the effect of ontogenetic variability on essential oil components, the full flowering stage was more effective in H. perforatum and H. aucheri species (Pasa, 2013). The amount of essential oil and the changes in its chemical composition during ontogenesis are specific to each taxon (Németh, 2005). The findings from previous studies showed that there may be similarities and differences in the its chemical composition and amount of essential oil of various species at different phonological stages or harvesting time inMenhta aquatic L. (Andro et al., 2013), Origanum vulgareL. (Chauhan et al., 2013), Ocimum basilicum L. (Lemberkovics et al., 1998), Cuminum cyminum L. (Moghaddam et al., 2015), andThymus capitatus L. (Casiglia et al., 2015).
The timing of the harvest or collection of the herbal crops is one of the most important factors affecting the quality of the essential oils obtained from them. The therapeutic properties of herbal drugs are related to the bioactive substances they contain. The amount of bioactive substances composed of secondary metabolites shows significant changes according to the development stage of plant. For this reason, the drug producer must first of all know the bioactive substance exchange of the medicinal and aromatic plant very well and gather the drug which is the richest of the active substances (Baydar, 2013). Essential oils are the most important of other volatile secondary metabolites derived from medicinal and aromatic plants. Therefore, obtaining high essential oil yields with the most desirable chemical compounds is very important for industrial purposes. The selection of appropriate phonological stage can be help researchers to fulfill this requirement (Afshari & Rahimmalek, 2018).
In the dry capsules, 0.087±0.015% essential oil was detected. In the obtained essential oil, 23 components were determined, which make up 99.50% of the essential oil. α-Pinene had the highest value with 33.28% among these components. This component was followed by β-pinene (17.80%), β-myrcene (9.30%), limonene (5.95%), and cis-ocimene (5.45%), respectively. In addition, trans-caryophyllene, α-terpineol, carvacrol, copaene, verbenone and trans- β -ocimene have been recorded as other important components (Table 7). No studies on the capsule essential oil content and composition of H. heterophyllum have been found in the literature review. The essential oils examined were found to be rich in the major components that exhibit various biological activities (Table 8).