关键词: 皱皮木瓜, 有机酸, 气相色谱-质谱联用仪, 特征性成分, 变化规律

Abstract:

【Objective】 The study was carried out to identify characteristic organic acids and disclosing their dynamic changing law of Chaenomeles speciosa fruit from Qijiang, Chongqing during its fruit developing period, so as to provide the basic data for the C. speciosa fruit organic acids metabolic research. 【Method】 By methanol extracting, methyl derivating and GC-MS detecting, the organic acids composition and their content of 8 developing period C. speciosa cv. Daluo fruit samples of Qijiang was measured. The 2012 chromatographic similarity analysis software of Chinese Pharmacopoeia Commission was used to match their common constituent peaks. The dynamic law of the total organic acids, strong-sour and weak-sour organic acids were showed in SigmaPlots10.0 software and the PCA and HCA of all the samples was processed separately by Simca-P 11.5 and SPSS 20.0 softwares. 【Result】 The total 41 common characteristic constituents, including 10 short-chain carboxylic acids, 21 long-chain fatty acids, 5 aromatic-organic acids, 3 monobasic-phenol acids and 2 amino-acids, were successfully matched among 8 TICs of different period fruit samples C. speciosa cv. Daluo from Qijiang. The baseline of all the TICs were smooth and stable, the organic acid derivatives peaks' distribution were well-distributed, and the separating-degree of samples’ peaks was high. All target components were well separated. The total organic acids content of Qijiang C. speciosa cv. Daluo fruit from 90 ^th day after its full-bloom stage to 160 ^th days showed the changing on reversed ‘Z’ that including the sharply decreasing, slowly increasing and then decreasing again. The total organic acids content was significant positive correlated with the strong sour (r=0.970) and the weak sour taste organic acids (r=0.998). At the same time, the strong sour taste organic acids were significant positive correlated with short-chain carboxylic acids (r=0.999) and positive correlated with monobasic phenol acids (r=0.747). The weak sour taste organic acids were significant positive correlated with long chain fatty acids (r=0.999). The malic acid, laevulic acid and citric acid, whose relative content sum was more than 90%, were the key ingredients of strong sour organic acids. The malic acid content had experienced a reverse ‘Z’ trend that decreased firstly (90 ^thd-120 ^thd), increased slightly (120 ^thd-130 ^thd) and decreased finally (130 ^thd-160 ^thd). The citric acid had a similar process, but the levulic acid had an obviously reverse process of changing with malic acid. Actually the levulic acid showed the increasing progress gradually. The correlation analysis showed that the strong sour taste organic acids had significant positive correlation with malate and citrate, but weakly negative correlation with levulic acid, isocitric acid, and salicylic acid. The analyzing result showed that most of the weak sour organic acids including 9-octadecenoic acid, 9,12-octadecadienoic acid, hexadecanoic acid and 10-hydroxy-hexadecanoic acid experienced the similar accumulating progress which was rapidly decreasing firstly, then slowly increased and decreased in the final stage. However, nonadecanoic acid showed an opposite process that was gradually increasing. Correlation analysis showed that the total weak sour organic acids were positively related to most of them such as 9-Octadecenoic acid and 9, 12-Octadecadienoic acid but negative to nonadecanoic acid. The PCA result by Simca-p 11.5 disclosed that PC1 and PC2 separately distributed 40.00% and 23.20% of the total variance contribution rate. The main component score of each sample showed that: S1 and S2 clustered together which decided by α-Ketoglutaric acid, malic acid, quinic acid, shikimic acid, hexadecanoic acid and linoleic acid. The S3, S4 and S5 got into one branch that mainly because of oleinic acid and 10-hydroxy-Hexadecanoic acid. The S6 was closer to S7 largely because of malonic acid, levulic acid, isocitric acid, salicyluric acid. The S8 formed a unit alone that mostly decided by succinic acid, nonadecanoic acid, tetracosanoic acid. This result was very similar to the other one that clustered by Ward's method with Squared Euclidean Distance in SPSS. 【Conclusion】 C. speciosa cv. Daluo in Qijiang,Chongqing is a typical malate-accumulating fruit. During its developing period of C. speciosa fruit, the accumulating pattern of organic acids changed from Malate-Citrate accumulating type on 90 ^th days to Levulinic acid-Malic acid - Citric acid accumulating type on 160 ^th days after its flower-blooming. The change of acid accumulation pattern played a key role in the determination of acidity and flavor quality of C. speciosa fruit in Chongqing.

Key words: Chaenomeles speciosa cv. Daluo, organic acids, GC-MS, fruit developing period, changing law