番石榴多酚氧化酶的部分纯化及其特性研究

番石榴PPO的粗提取液经过80%硫酸铵盐析和DEAE-Toyopearl 650M、CM-Sephadex C-50离子交换柱层析分离后,被纯化了约126倍,回收率为16.13%。该酶迅速地催化焦性没食子酸的酶促氧化反应,而对对苯二酚和绿原酸则完全无催化活性。该酶对焦性没食子酸的Km值为4.6 mmol/L,其最适pH为7.5,pH稳定性范围在pH4.0~11.0,最适温度为50℃,热稳定性相对较高,在≥90℃加热10 min后仍残留约15%的酶活性。该酶的最佳抑制剂是抗坏血酸和NaHSO3,其次是植酸、盐酸-L-半胱氨酸、柠檬酸,Ca2+、Mg2+等金属离子对该PPO也有较强的抑制作用。     

Effect of Guava (Psidium guajava L.) Leaf Extract on Glucose Uptake in Rat Hepatocytes

ABSTRACT:  People in oriental countries, including Japan and Taiwan, boil guava leaves ( Psidium guajava L.) in water and drink the extract as a folk medicine for diabetes. The present study investigated the enhancement of aqueous guava leaf extract on glucose uptake in rat clone 9 hepatocytes and searched for the active compound. The extract was eluted with MeOH-H₂O solutions through Diaion, Sephadex, and MCI-gel columns to separate into fractions with different polarities. The uptake test of 2-[1-¹⁴C] deoxy-D-glucose in rat clone 9 hepatocytes was performed to evaluate the hypoglycemic effect of these fractions. The active compound was identified by nuclear magnetic resonance analysis and high-performance liquid chromatography (HPLC). The results revealed that phenolics are the principal component of the extract, that high polarity fractions of the guava leaf extract are enhancers to glucose uptake in rat clone 9 hepatocytes, and that quercetin is the major active compound. We suggest that quercetin in the aqueous extract of guava leaves promotes glucose uptake in liver cells, and contributes to the alleviation of hypoglycemia in diabetes as a consequence.     

Polyphenoloxidase from guava (Psidium guajava L.)

Polyphenoloxidase (PPO) was isolated from guava (Psidium guajava L., cv. Kampuchea). Purification by acetone precipitation and dialysis of the Amicon concentrate resulted in 4.9-fold and 17.2-fold purification of the dialysed crude extract respectively. Polyacrylamide gel electrophoresis indicated that PPO had a molecular weight in the region of 120000–140000. The pH optimum of the enzyme was found to be 7.2. Heat inactivation studies showed that heating for 1.1, 3.5, and 10.1 min at 75, 65 and 55°C respectively caused a 50% loss in enzymic activity. The enzyme-catalysed browning reaction was significantly inhibited in the presence of sodium metabisulphite, L-cysteine hydrochloride and ascorbic acid.     

Kinetics of Crude Peroxidase Inactivation and Color Changes of Thermally Treated Seedless Guava (Psidium guajava L.)

Thermal treatment of seedless guava (Psidium guajava L.) cubes was carried out in the temperature range of 80–95 °C. The kinetics of peroxidase inactivation and color changes due to thermal treatments were determined. Peroxidase inactivation followed a first-order kinetic model, where the activation energy was 96.39 ± 4 kJ mol⁻¹. Color was quantified in terms of L, a, and b values in the Hunter system. The color changes during processing were described by a first-order kinetic model, except total color difference which followed a zero-order kinetic model. The temperature dependence of the degradation followed the Arrhenius relation. The activation energies (E _a) for L, a, b, and total color difference (ΔE) were 122.68 ± 3, 88.47 ± 5, 104.86 ± 5, and 112.65 ± 5 kJ mol⁻¹, respectively. The results of this work are a good tool to further optimize seedless guava thermal treatment conditions.     

DPPH自由基比色法测定番石榴叶提取物抗氧化活性的研究

本文用2,2-联苯-1-三硝基苯肼(DPPH·)比色法测定了番石榴叶(PsidiumguajavaL.)的抗氧化活性,并使用了三个不同参数抑制率、EC50和AE来评价其抗氧化活性。结果表明,浓度越高,番石榴叶提取物清除自由基的能力越强,其中AE是表示抗氧化活性的最有效的能数。本研究表明番石榴叶提取物是一种有效的、有开发价值的天然抗氧化剂。     

Physico-chemical changes in guava (Psidium guajava L.) during development and maturation

Guava of the Vietnamese variety is commercially grown in Malaysia. To obtain a better understanding of the fruit, the physical and chemical changes occurring during development and maturation were studied. The weight increase, reduction in hardness, total pectin content, and changes in glucose and ascorbic acid levels showed a sigmoid curve. The maximum weight and glucose increases occurred between weeks 10 and 12. Reduction in hardness, and changes in pectin and ascorbic acid content occurred most between weeks 12 and 14. Reduction in chlorophyll content, and increase in fruit diameter, fructose content and water soluble pectin fraction showed a more linear change. Fructose level was highest among the three sugars (fructose, glucose and sucrose) monitored during maturity. The density of the fruit increased rapidly at the beginning, remained constant between weeks 4 and 12 and then decreased again. The moisture content increased rapidly at first, followed by a more gradual increase and remained constant after week 14. The pH and percentage titratable acidity of the Vietnamese guava fluctuated, being fairly acidic at week 4 (pH 4.5), least acidic at week 10 (pH 5.4) and acidic again on maturity (pH 4.05). The tannin level was high in immature guava but dropped drastically after week 8, and remained at a constant low level after week 10. Soluble pectin increased during development and maturity. Insoluble pectin (NaOH soluble) increased during development but was converted to soluble pectin during maturity (after week 14).     

“珍珠”番石榴的营养成分与挥发性风味特征分析

探索热带水果珍珠番石榴的营养及风味特色,对其基本成分进行测定,并利用感官描述分析(QDA)和SPME—GC—MS对风味进行探讨,为其保藏和深加工提供理论依据。结果表明:珍珠番石榴中水分、总糖、还原糖、总酸、粗蛋白、灰分、Vc等基本成分的含量分别为84.79,9.21,3.85,0.56,0.82,0.74,0.13g/100g;感官风味表现为清甜爽脆,香味浓郁,具有鲜明的番石榴风味特色;SPME—GC—MS分析检出41种挥发性风味成分,其中酯类和醛类物质占总量的85.06%,对珍珠番石榴的风味有重要贡献。     

Volatile constituents from a guava (Psidium guajava L.) natural flavour concentrate

The volatile constituents of a commercially produced guava natural flavour concentrate were isolated by simultaneous distillation-extraction with diethyl ether. The resultant essence was analyzed by capillary gas chromatography and GC-MS technique. A total of 29 compounds was identified, from which 10 substances could be described for the first time as guave fruit constituents.     

Effect of Extraction Techniques and Solvents on Antioxidant Activity of Pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.) Leaf and Stem

The effect of commonly used techniques and solvents in the antioxidant activities of Pomegranate leaves and stems were studied. The extraction techniques compared were successive, individual (cold percolation), and decoction methods in both parts using solvents viz. petroleum ether, toluene, ethyl acetate, acetone, and water. The antioxidant activity of all the different solvent extracts of leaves and stem was evaluated using antioxidant assays like 2,2-diphenyl-1-picryl hydrazyl free radical scavenging assay, superoxide anion radical scavenging assay and ferric-reducing antioxidant power. Total phenol and flavonoid content was also measured. Successive extraction was a better technique to extract the antioxidants from pomegranate than other techniques evaluated in the present study. For the aqueous extraction, decoction method was found to be the best method to extract the antioxidants and it is the most convenient, exhaustive, and time-saving extraction technique for both parts of pomegranate. The results showed that the extracting solvent significantly altered the antioxidant property estimations of pomegranate leaf and stem. High correlations between phenolic compositions and antioxidant activities of pomegranate extracts were observed. High levels of antioxidant activities were detected in pomegranate leaf as compared to stem indicating that the leaf may serve as an excellent source of natural antioxidants.     

番石榴籽油提取工艺优化

采用索氏提取法并通过单因素试验和L9(33)正交试验对番石榴籽油的提取工艺进行了优化。结果表明,影响番石榴籽油提取的主要因素顺序为温度、提取时间、料液比。优化工艺为：溶剂石油醚、提取温度90℃、提取时间3h、料液比1:10(g/ml); 此工艺条件下的出油率为12.82%。     

9个品种番石榴果实提取物抗氧化活性比较研究

目的 分析比较9个品种番石榴果实的抗氧化活性,为筛选适合开发天然抗氧化产品的番石榴优良品种提供理论依据。方法 测定‘紫色’‘红宝石’‘粉红蜜’‘西瓜’‘珍珠’‘帝王’‘翠玉’‘水蜜’‘本土’9个品种番石榴醇提物和水提物的总酚、黄酮含量,研究其对2,2’-联氮-双(3-乙基苯并噻唑啉-6-磺酸)二铵盐[2,2’-azino-bis（3-ethylbenzothiazoline-6-sulfonicacid）ammonium salt, ABTS]、1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl, DPPH）自由基清除能力和总抗氧化能力,利用抗氧化能力综合指数评价不同样品的抗氧化活性,并分析总酚、黄酮含量与抗氧化活性的相关性。结果 9个品种番石榴醇提物总酚和黄酮含量分别为1.363~2.394 g/100 g和0.607~1.875 g/100 g,对DPPH、ABTS自由基的半数清除浓度（medium inhibition concentration, IC50）分别为0.242~0.518 mg/mL和1.990~4.929 mg/mL,总抗氧化能力为0.113~0.206 mmol/g;水提物总酚和黄酮含量则为1.192~2.142 g/100 g和0.393~1.118 g/100 g,对DPPH、ABTS自由基的IC50分别为0.320~0.661 mg/mL和2.837~5.472 mg/mL,总抗氧化能力为0.105~0.181 mmol/g。水提物和醇提物的总酚、黄酮含量均以‘紫色’番石榴最高,抗氧化能力综合指数也以‘紫色’最高。除‘水蜜’外,其他品种醇提物的抗氧化活性均高于水提物。相关性分析结果显示,总酚、黄酮含量与DPPH自由基清除能力、ABTS自由基清除能力、总抗氧化能力和抗氧化能力综合指数呈正相关关系。结论 9个品种番石榴的提取物中,‘紫色’醇提物的总酚、黄酮含量和抗氧化活性最高,是开发天然抗氧化产品的最佳来源。     

番石榴和番石榴叶加工研究进展

综述了番石榴及番石榴叶的化学成分及其功效,阐述和分析了番石榴及番石榴叶中有效成分的提取方法,总结了番石榴果酒、番石榴饮料、番石榴果糕、番石榴果冻等番石榴加工技术研究进展,并讨论了其在食品工业中的加工利用前景。      

Changes in odour-active compounds of two varieties of Colombian guava (Psidium guajava L.) during ripening

Changes in the concentrations of odour-active compounds in two varieties of Colombian guava (Psidium guajava L.) fruits during ripening were followed by application of stable isotopic dilution analyses (SIDA). The data revealed that, in particular, the concentration of C₆-aldehydes, as well as the amount of the sulphur compounds 3-sulphanylhexyl acetate and 3-sulphanyl-1-hexanol, decreased with ripening, while the concentrations of aliphatic esters and furanones increased during this process. A calculation of odour activity values indicated that although the C₆-aldehydes decreased during ripening, these still made the greatest contribution to the overall aroma at all stages of ripening. Changes in odour-active compounds in white- and pink-fleshed guavas showed the same behaviour.     

番石榴叶多糖超声波细胞粉碎辅助提取工艺及其体外抗氧化活性

以番石榴叶为原料,采用超声波细胞粉碎法辅助提取番石榴叶多糖,探讨各因素对番石榴叶多糖得率的影响,通过Box-Behnken响应面法设计优化番石榴叶多糖的最佳提取工艺。通过测定·OH、DPPH自由基、O2-·的清除能力和总还原力,评价番石榴叶多糖体外抗氧化活性。结果表明,番石榴叶多糖的最佳提取工艺：料液比1∶14（g/mL）,超声功率140 W,提取时间16 min,此条件下番石榴叶多糖得率可达（2.00±0.08）%。提取后的番石榴叶多糖具有一定的体外抗氧化活性,其·OH清除率为（23.30±1.29）%,DPPH自由基清除率为（65.43±2.56）%,O2-·清除率为（22.30±1.53）%,具有较强的总还原力。     

Effect of Extraction Techniques and Solvent Systems on the Extraction of Antioxidant Components from Peanut (Arachis hypogaea L.) Hulls

This research work was carried out to investigate the effect of different extraction techniques on antioxidant potential of peanut (Arachis hypogaea) hulls. The antioxidant extracts of peanut hulls (PH) were prepared using different extraction methods such as soaking, stirring, shaking, and sonicated-assisted stirring with methanol/water (80:20) and ethanol/water (80:20) solvents systems. The antioxidant potential of extracts was measured using different in vitro antioxidant assays like estimation of total phenolic contents (TPC), estimation of total flavonoids contents (TFC), DPPH-scavenging capacity, percentage inhibition of linoleic acid peroxidations, and bleachability of ?-carotene in linoleic acid system. TPC and TFC of different PH extracts were found in range of 1.23–8.43 mg/g of dry plant material, measured as gallic acid equivalent, 0.33–5.06 mg/g of dry plant material, measured as catechin equivelent (CE), respectively. All the PH extracts exhibited good free radical scavenging potential and moderate inhibition of linoleic acid peroxidation. Significant (p ≤ 0.05) variations were observed in the antioxidant potentials of various extraction methods and solvent systems. Among all the extraction methods, sonicated-assisted stirring showed better yield and antioxidant capacity. In view of the present findings, it is reasonable to say that different extracts of peanut hulls exhibited varying degree of antioxidant activity, which might be attributed to various mechanisms involved in extraction procedures.     

Characterisation of the carotenoids and assessment of the vitamin a value of Brasilian guavas (Psidium guajava L.)

The carotenoids of guava cultivar IAC-4 from the State of Sõ Paulo (southeastern Brasil) were identified as β-carotene, ζ-carotene, γ-carotene, zeinoxanthin, lycopene, 5,6,5′,6′-diepoxy-β-carotene and 5,8-epoxy-3,3′,4-trihydroxy β-carotene. The principal pigment was lycopene, corresponding to 86% of the total carotenoid content (62 μg/g). β-carotene was present at 3·7 μg/g; consequently, the vitamin A was relatively low (617 IU/100g). The same carotenoids were encountered in guavas from the States of Ceará and Pernambuco (northeastern Brasil). Cis-γ-carotene and 5,8-epoxy-zeinoxanthin were also found in the samples from Pernambuco. While the lycopene contents of the northeastern fruits were equal to, or lower than, that found in guava IAC-4, the β-carotene level (5·5–11·9 μg/g) was higher, corresponding to higher vitamin A values (917–1983 IU/100 g). With respect to vitamin C, the amount detected in guava cultivar IAC-4 was much higher (97·7 mg/100 g) than those encountered in the northeastern guavas (9·2–52·2 mg/100 g).     

Evaluation and utilization of guava seed meal (Psidium guajava L.) in cookies preparation as wheat flour substitute

Guava seeds were chemically evaluated for their moisture, fat, protein, ash, fibre and minerals content. The fatty and amino acids composition was also studied. Guava seed meal was used in the preparation of cookies. Chemical composition, dough characteristics as well as cookies baking quality were studied to evaluate its possible utilization. The water absorption, dough development time and stability were decreased and dough weakening was increased as the level of guava seed meal in the dough increased. Adding guava seed meal to wheat flour improved volume, specific volume, diameter and thickness of the cookies after baking. Using 9% guava seed meal gave an acceptable, but comparatively inferior product.     

番石榴多糖化学与生物活性研究进展

番石榴（Psidium guajava）为桃金娘科植物,在全球热带及亚热带地区广泛种植。番石榴具有良好的食用和药用价值,长期被用于腹泻、糖尿病等疾病的辅助治疗。多糖是番石榴中的重要活性成分,具有抗氧化、抗肿瘤、抗炎、调节免疫、降血糖、改善肠道微生态等作用。该文对已报道的番石榴多糖提取方法、结构表征及生物活性相关研究进行梳理与总结,以期为番石榴及其多糖类成分在食品及医药领域的进一步开发利用提供参考和借鉴。