Mateja Colaric

Phenolic compounds in the fruit of different varieties of Chinese jujube (Ziziphus jujuba Mill.)

Summary Chinese jujube (Ziziphus jujuba Mill.) fruit were harvested at the fully mature stage from orchards in China in 2004, sundried and later investigated for their phenolic fingerprints. Phenolics were extracted from the following seven varieties of Z. jujuba Mill.: ‘Bianhesuanzao’, ‘Yuanlingzao’, ‘Fupingdazao’, ‘Zanhuangdazao’, ‘Zizao’, ‘Huizao’, and ‘Jinsixiaozao’, and from a variety of acid jujube [Z. jujuba Mill var. spinosa (Bunge) Hu et H. F. Chou]. Two phenolic acids from the hydroxycinnamate sub-class (chlorogenic acid and caffeic acid) and three flavonoids (catechin, epicatechin and rutin) were determined by high-performance liquid chromatography in extracts of dried Chinese jujube fruit. Among the varieties, considerable differences in the contents of each phenolic compound were confirmed. Acid jujube fruit had the highest content of hydroxycinnamic acids, as well rutin and epicatechin, while ‘Zizao’ had the highest catechin content. Consequently, acid jujube was the richest source of phenolics (i.e., the sum of all phenolics analysed was the highest), while ‘Jinsixiaozao’ was the poorest source. Jujube fruit were a good source of phenolics (especially flavonoids), comparable to prunes, and therefore should be recommended by nutritionists to be part of our diet.

Changes in sugars and phenolics concentrations of Williams pear leaves during the growing season

Leaves of Williams pear were collected during the growing season from May to October and the contents of sugars and phenolic compounds were analyzed by high-performance liquid chromatography method. Sorbitol was the major sugar (up to 83.8 g kg-1 DW), followed by sucrose (up to 22.1 g kg-1 DW). Concentrations of glucose and fructose were as high as 12.9 and 9.0 g kg-1 DW, respectively. Leaves contained up to 29 471.9 mg kg-1 DW of chlorogenic acid, followed in concentration by rutin (up to 6789.2 mg kg-1 DW), epicatechin (up to 7378.0 mg kg-1 DW), catechin (up to 3846.5 mg kg-1 DW), vanillic acid (up to 1832.1 mg kg-1 DW), syringic acid (up to 1123.5 mg kg-1 DW), caffeic acid (up to 122.5 mg kg-1 DW) and sinapic acid (up to 94.1 mg kg-1 DW). The significant differences in concentration of sorbitol, sucrose, glucose, and in all analyzed phenolics were observed during the growing season (six sampling dates). The lowest concentrations in the leaf were found at the beginning of the growing season in May and J...

Primary metabolites in the leaves and fruits of three pear cultivars during the growing season

Primary metabolites (sugars and organic acids) in leaves and fruits of the pear cultivars Conference, Concorde and Williams were investigated during the growing season in Slovenia. Leaves were sampled 15 times from Apr. 25 to Oct. 22. Fruits were sampled seven times from Jun. 14 to Aug. 23. The contents of sugars (glucose, fructose, sucrose, and sorbitol) and organic acids (malic, citric, shikimic, and fumaric) in leaves and fruit were determined by high performance liquid chromatography (HPLC). Similar dynamic patterns were found in the glucose, fructose, sucrose and sorbitol in leaves and fruits of the genetically related cultivars Conference and Concorde. Leaf sugar was low at the beginning of the growing season when the leaves were not completely developed. Generally when sucrose increased in leaves it decreased in fruits. At the end of June the total sugar content in leaves reached its peak then rapidly decreased. At the same time, total sugar in fruits increased. From the beginning of August, total ...

Bending affects phenolic content of William pear leaves

Abstract The effect of branch bending on the phenolic content in pear leaves was investigated. Leaves were sampled from the tree branches which were bent in summer 2003 (1 September), in spring 2004 (15 May), and from unbent trees. Samplings were made during the growing season May to October 2004, on the following dates: 1st sampling, 15 May; 2nd sampling, 11 June; 3rd sampling, 9 July; 4th sampling, 6 August; 5th sampling, 2 September; and 6th sampling, 1 October. The leaves contained caffeic acid, chlorogenic acid, sinapic acid, syringic acid, vanillic acid, rutin, epicatechin and catechin. The lowest contents of phenolics were found on the first occasion. After that, in the sequence of sampling dates, an increase was noticed at first, but after reaching their highest point, the contents of phenolics decreased. In most cases fewer contents of phenolic compounds were found in leaves from bent branches (especially from branches bent in summer), and the highest ones in leaves from the control group. For all phenolics, apart from the caffeic and vanillic acids, significant differences were evident among treatments, with the highest contents in the control group and almost the lowest in the summer treatment. It is suggested that the change in branch angle caused the physiological response of pear tree, with different contents of phenolic compounds in its leaves from bent and non-bent branches.

Effects of branch bending on the levels of carbohydrates and phenolic compounds in ‘Conference’ pear leaves

Summary The effects of bending on carbohydrates and phenolic compounds were investigated in ‘Conference’ pear leaves during the growing seasons in 2004 and 2005. Leaves were sampled from tree branches bent in the late-Summer of 2003, in Spring 2004, and from unbent branches. Levels of carbohydrates (i.e., sucrose, glucose, fructose and sorbitol) and phenolic compounds (i.e., chlorogenic acid, sinapic acid, vanillic acid, (+)-catechin, (–)-epicatechin, rutin, quercetin-3-D-galactoside and quercetin-3-βD-glucoside) were determined in pear leaves using high performance liquid chromatography. In the first sampling year, significantly higher contents of some of the phenolics measured (i.e., chlorogenic acid, vanillic acid, sinapic acid, and rutin) were observed in leaves from the Spring treatment. In the second year, a similar tendency among treatments was significant at the September and October sampling dates for chlorogenic acid and vanillic acid, and at one sampling date in October for catechin and one in September for quercetin-3-D-galactoside. In June and August 2004, epicatechin and catechin levels, respectively, were significantly higher in the controls. In May and June 2005, quercetin-3-D-galactoside and sinapic acid, respectively, exhibited significantly higher values in the controls. Quercetin-3-βD-glucoside was highest in control leaves in May, June, July and October. In August 2004, significantly higher contents of epicatechin were found in leaves from the Summer treatment. Carbohydrate levels showed no clear tendency among treatments, as did some phenolics. During our research, the patterns of carbohydrates and phenolics were also ascertained over the growing season. In general, in 2004, the levels of phenolics increased, then decreased over the growing season. In 2005, however, the maximum levels of phenolics were reached earlier, then, after decreasing, another increase occurred from August to October. Moreover, it was found that sorbitol predominated among the carbohydrates, and chlorogenic acid predominated among the phenolics in both growing seasons. These are the first data on variations in carbohydrate and phenolic contents in pear leaves, as influenced by branch-bending over two successive years. These variations appear to result from the physiological response of pear trees and leaves to this cultural practice.