Study On Chemical Constituents And Biological Activities Of Juniperus Przewalskii At Different Altitudes

Juniperus przewalskii(Cupressaceae)is the evergreen tree.It is often used as afforestation tree species in some areas of China and as medicinal plant of Tibetan medicine,so it has important ecological and medicinal value.At present,systematic studies on the chemical compositions and biological activities of Juniperus przewalskii at different altitudes have not been reported.This study is based on the Juniperus przewalskii leaves at different altitudes of Maixiu Forest Farm in Zeku County and Zhongtie Forest Farm in Xinghai County of Qinghai Province,from the perspective of essential oils and phenolic compounds of Juniperus przewalskii leaves,the differences of chemical composition and content,antibacterial activity and antioxidant activity were analyzed.Based on these,the GC-MS fingerprint and HPLC fingerprint combined with chemometrics was performed,the classification and the unknown source identification mode of Juniperus przewalskii at different elevation gradients were also constructed.The essential oil and phenolic compounds of Juniperus przewalskii leaves at different altitudes in the two regions were identified.Screening out the elevation area of Maixiu Forest Farm and the Zhongtie Forest Farm can be used as the source of excellent quality of Juniperus przewalskii,and find out the key compounds for quality evaluation and control.The main conclusions are as follows:1.The essential oils and phenolic compounds of Juniperus przewalskii leaves at different altitudes were analyzed.(1)The compounds of essential oils were significantly different at different altitudes.The yield of essential oil was highest at 3400m(3.27%)of Maixiu Forest Farm;a total of 95 compounds were detected,and the total content of essential oil compound was highest at 3192m(82.92%).The yield of essential oil was highest at 3400m(3.83%)of Zhongtie Forest Farm;a total of 55 compounds were detected,and the total content of essential oil compound was highest at 3200m(85.62%).The total content of essential oil increased first and then decreased with increasing altitude(2)The phenolic compounds were significantly different at different altitudes.The highest of total phenolic content(6.61±0.11 mmol equiv.GAE/g)and total flavonoids content(0.56±0.05 mmol equiv.GAE/g)is 3300 m of Maixiu Forest Farm,while the highest total content of phenolic compound is 3400m(9.05±0.15 mg/g).The highest of total phenolic content(6.49±0.14 mmol equiv.GAE/g)and the total content of phenolic compounds(8.03±0.15 mg/g)is 3400 m of Zhongtie Forest Farm,while the highest total flavonoid content is altitude of 3200m(0.69±0.08 mmol equiv.GAE/g).The total content of phenolic main compounds increased with increasing altitude.2.The antibacterial activity and antioxidant activity of essential oils and phenols of Juniperus przewalskii leaves at different altitudes were evaluated.Combining both sides,the biological activity was the best at 3300 m of the Maixiu Forest Farm and 3400 m of Zhongtie Forest Farm.The biological activity decreased with increasing altitude.3.The GC-MS fingerprints and HPLC fingerprints of Juniperus przewalskii at different altitudes in Maixiu Forest Farm and Zhongtie Forest Farm were constructed,and then a comprehensive analysis was carried out by chemometrics.Through HCA,PCA and DA,the classification of Juniperus przewalskii at different altitudes in Maixiu Forest Farm and Zhongtie Forest Farm were clarified,and the prediction model for unknown samples was established.The key compounds for the quality evaluation of essential oil in Juniperus przewalskii leaves were sabinene,and the key compounds for the quality evaluation of phenolic compounds were amentoflavone and quercitrin.4.The composition and content,biological activity,fingerprint and stoichiometric analysis of essential oil and phenols of Juniperus przewalskii leaves were analyzed,it was concluded that the 3192 m of Maixiu forest farm and the 3400 m of Zhongtie forest farm could be used as the best quality elevation area of Juniperus przewalskii.