| Rubus chingii Hu is the plant-source of medicine and edible "fu-pen-zi",which has been used as medicine for a long history in China.Studies have shown that its branches and leaves also have a certain medicinal value.However,there are few reports on related development and utilization.Pruning is often required every year when branches and leaves are replaced,and a large number of branches and leaves are directly discarded.Reasonable utilization of the leaves is helpful to the comprehensive development of R.chingii Hu.Therefore,the spectrophotometry and high performance liquid chromatography-mass spectrometry were used to systematically study the phenolic components and antioxidant activities of different parts(fruits,stems,tender leaves,and old leaves)so as to provide certain data support for the developing and utilization of stems and leaves.Simultaneously,the chemical composition and antioxidant activity of the young and old leaves at different harvesting periods were analyzed,and the appropriate harvest time was determined.And on this basis,the production process of leaf tea was initially explored for further extending the industrial chain and for enhancing its economic added value.The main results are as follows:1.A comparative study of total phenol,total flavonoids and proanthocyanidins in different parts of R.chingii was performed,and the total phenol content of tender leaves,the total flavonoid content of old leaves and the proanthocyanidins content of fruits were the highest,respectively.The composition of phenolic compounds in tender and old leaves is similar,mainly kaempferol derivatives and quercetin derivatives,which are significantly different from flavonoids in fruits and stems.Tender leaves have the strongest antioxidant activity,followed by old leaves and stems,and fruits have the weakest antioxidant activity.Correlation analysis showed that total phenol contributed the most to antioxidant activity.It can be seen that the phenolic compounds of tender leaves can be used as potential sources of natural antioxidants and have certain development potential for health products.2.The dynamic analysis of the chemical composition of the tender leaves and old leaves of different harvesting periods was carried out,and it was found that the content of total phenol,total flavonoids,soluble sugars and other components in the young leaves and old leaves of R.chingii were significantly different.,Total flavonoids,soluble sugar,soluble protein and free amino acid contents were highest in September,June,August,July and March separately;The content of old leaves above indicators was highest in April,September,June,June and April.From March to August,the total flavonoids,total phenols and soluble protein content of tender leaves showed a trend of first increasing and then decreasing,while soluble sugar showed an increasing trend,and the change trend of old leaves was roughly the opposite;The soluble protein and total phenol showed a decreasing trend,and soluble sugar and flavonoids showed an upward trend;the soluble protein and total flavonoids of old leaves changed first and then increased,while the total phenol and soluble sugar content changed the opposite direction from from September to November.HPLC analysis showed that the content of kaempferol-3-O-rutinoside in the young leaves was the highest in April,followed by August,and the lowest in May;while the content of tiliroside was the highest and the lowest in April and November,respectively.The total content of the two types of ingredients reached its highest in August.The contents of kaempferol-3-O-rutinoside and tiliroside in old leaves were generally lower than those in tender leaves,and thecontents of lindenside were not detected in some months.Through comprehensive analysis of the content of various nutrients and biological active ingredients,it is concluded more appropriate to pick tender leaves in August.3.The antioxidant activity of tender leaves and old leaves at different harvesting time were studied,and it was found that the DPPH free radical scavenging rate of tender leaves was the highest in August,and the ABTS+ˇfree radical scavenging rate was higher in May and September.The FRAP total reducing power of tender leaves was higher in June,August and September.It can be seen that the tender leaves have stronger antioxidant capacity in August and September.Compared with tender leaves,the DPPH,ABTS+ˇfree radical scavenging rate and FRAP total reducing power of old leaves at different harvesting times were consistent,which indicated that the old leaves had higher antioxidant activity in April.Therefore,if antioxidant activity is used as an indicator,tender leaves are suitable for harvesting in August and September,while old leaves are suitable for harvesting in April.4.By imitating the green tea processing technology,the spreading,heating and drying processes of leaf tea processing were explored,and the inherent quality of leaf tea was comprehensively evaluated with multiple indicators such as free amino acids,water extracts,tea polyphenols,soluble sugar and total flavonoid.Firstly,the leaf were inspected at different spreading time,and it was found that the quality of the leaf prepared at the spreading time of 6h was good.Then,three different methods of microwave heating,steam heating and blanching heating were investigated.It was found that the contents of water extracts,total flavonoids and tea polyphenols of leaf by microwave heating were the highest;soluble sugar and free amino acid content were slightly were lower than those of steam by steam heating,however,the chemical composition was the lowest by blanching heating.After comprehensive analysis,the quality of the leaf by microwave heating is good,so microwave heating could be used as a green removing method for leaf of R.chingii.Then the hot-air drying,microwave drying and vacuum freeze-drying were used to treat the twisted leaves,and it was found that the content of each chemical component under vacuum freeze-drying conditions was the highest,followed by microwave drying.And the content of each chemical component after hot air drying were the lowest.Based on the analysis of tea sample quality and drying cost,microwave drying is the most suitable method.Therefore,it can be preliminarily determined that the processing technology of leaf of R.chingii is:fresh leaf picking-spreading 6h-microwave heating-microwave drying. |
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