Major Antioxidants and In Vitro Antioxidant Capacity of Eleven Mango (Mangifera Indica L.) Cultivars

Abstract

Eleven mango cultivars which were cultivated popularly in China were selected as materials in this study. The ascorbic acid, α-tocopherol, total carotenoid, total ployphenol, total flavonoid, and mangiferin contents, and in vitro antioxidant capability of the fruit pulp were tested for comparison of individual cultivars. Comparisons of parameters were further conducted after dividing all cultivars into three groups, i.e., red (Zill, Zillate, Renong No. 2, Keitt and Lippens), green (Guire No. 82, Yuexi No. 1 and Zihua) and yellow (Chunhuang, Renong No. 1 and Tainong No. 1) in peel color. The results showed that antioxidant contents and in vitro antioxidant capabilities varied among cultivars and among groups. Guire No. 82 had the highest total polyphenol and flavonoid contents; Renong No. 1 showed a dramatically large value of α-tocopherol content; and green peel mangoes accounted for higher ascorbic acid, total polyphenol, total flavonoid contents, and total in vitro antioxidant capability. Besides, correlation analysis and principal component regression analysis indicated that antioxidants (except α-tocopherol) were positively correlated to total in vitro antioxidant capacity; polyphenolic chemicals were deemed to be one of the most critical factors affecting on total in vitro antioxidant capability.

Keywords:

• Mango
• Antioxidant
• Antioxidant capacity
• Correlation analysis
• Principal component regression analysis
• Cultivars

INTRODUCTION

Antioxidants are the chemical substances with the capability of inhibiting oxidation.^[1] Many of them, such as ascorbic acid, tocopherol, carotenoids, flavonoids, and polyphenols, have been well known by common people for their benefits to body immunity, anti-aging, beauty care, and so on.^[2,3] Natural antioxidants are presently arousing extensive attentions of medicine, nutrition, and fruit science circles, due to their significant curative effects on various diseases caused by free radicals.^[2−5] For example, curcumin and vitamin C could significantly reduce malondialdehyde level, restore the enzyme activities of superoxide dismutase and catalase, and modify the reduction of reduced glutathione level; curcumin have significant nephroprotective effects; quercetin-rich foods could protect against fluoride-induced hepatotoxicity.^[6−8] Thankfully, natural antioxidants are widely found in various fresh vegetables and fruits and supply populations in daily life.

Mango (Mangifera indica L.) fruit, popularly known as ‘King of Tropical Fruit’,^[9] is one of the most important fruits in terms of production, marketing, and consumption. Among tropical fruits, it ranks second to the banana in international trade.^[10] China serves as the second largest production country, slightly lower than 4 140 290 T in 2009. Mango pulp and concentrate juice in present international markets is widely use as a base material in beverage industry, as a flavoring ingredient in dairy industry, and in baby food formulations.^[10]

Mango fruit is not only rich in common nutriment, but also rich in natural antioxidants. According to the USDA,^[11] mango had a higher content of ascorbic acid, which was nine and four times that of the apple and banana, respectively. Similarly, its carotenoid content also held a big superiority, with nearly 10 times that of the apple or orange. α-tocopherol was another preponderant composition, which was more than 18 times that of the apple and outdistances that of the grape, orange, tangerine, and banana. Moreover, many previous studies have showed that those major antioxidants (i.e., vitamins, flavonoids, carotenoids, polyphenols, mangiferin, etc.) contribute directly to the total antioxidant capacity of mango.^[5,12−14] Thus far, a few reports have indicated that antioxidant properties differ in cultivar types.^[14−16] Antioxidant values were affected by many factors, including region separations, ripening degree at harvest, postharvest factors, determination methods, and character segregation in posterior generations, etc.^[12,17−19] Nevertheless, in previous studies, especially in the pharmaceutical industry, attentions had been more paid to the antioxidants of mango stem, leaf, peel, and seed kernel rather than pulp, the edible part,^[10,12,20] though with less antioxidants in it. In general, less is known about the antioxidants of mango pulp. Besides, peel color is of great importance for commercial value, but there are no reports on the antioxidant characteristics related to different peel-color mangoes. Furthermore, hundreds of mango cultivars have been generated by extensive breeding, which could bring diversities in fruit size, shape, color, flavor, seed size, and nutraceutical properties, especially antioxidant contents and in vitro antioxidant capability. It is therefore still a complex issue to characterize antioxidants properties in mango pulp. In this research, mango pulp of 11 cultivars were collected to measure the levels of six antioxidants and their total in vitro antioxidant capabilities; subsequently, correlations analysis and principal component analysis (PCA) were carried out to determine the critical factors in antioxidant capability. The objective was to get insight into the antioxidant characteristics in mango pulp of popular varieties in China, and to pave the road for further studies.

MATERIALS AND METHODS

Materials

Samples were taken according to Mo et al.^[21] with modifications. Mango fruit of 11 typical cultivars, i.e., Zill, Zillate, Renong 2, Keitt, and Lippens with red peel, Guire No. 82, Yuexi No. 1 and Zihua with green peel, and Chunhuang and Renong No. 1 and Tainong No. 1 with yellow peel, whose trees were grafted on 17-year-old rootstock Yuexi No. 1, were sampled from the same orchard located in Zhanjiang, Guangdong Province, China. For each cultivar, night trees with similar size and similar vigor were randomly selected and marked for sampling. Randomized block design was employed for each treatment with three replicates. Each replicate consisted of about 20 fruits from three individual trees.

Sample Preparation

During June–July 2010, the harvesting maturity stage, fruit at about 80% full ripeness and with identical size were picked and transported immediately to the laboratory for accelerating the ripening, i.e., rinsing with 0.05% ethephon and airing before storing at room temperature until complete ripening. About three days later, the fruit were full ripe and suitable for pulp collection. After being peeled and cut into small pieces, pulp was frozen by liquid nitrogen and ground into powder. All the homogenized pulp powder was immediately stored at –40°C for the subsequent analyses.

Ascorbic Acid Extraction and Measurement

Ascorbic acid was estimated by titrating sample extract, with 2,6-dichlorophenol indophenol dye solution, following the methods from GB/T6195-86 (Chinese National Standard), recommended by Association of Official Analytical Chemists (AOAC),^[22] with modifications. The volumetric titrant (2,6-dichlorophenol indophenol sodium solution) was standardized using the solution of reference substance, 0.02 mg mL⁻¹ ascorbic acid reagent. Two g powder of fresh pulp was added into 8 mL of 2% (w/v) oxalic acid for 8 min extraction under stirring. The mixture was centrifuged at 9000 × g for 10 min at 4°C (Universal 32 R, Hettich Inc., Germany). The supernatant was moved to a new test tube and 0.8 g kaolin was added to it for discoloration before filtrating. An aliquot of 5 mL filtrate was titrated with 2,6-dichlorophenol indophenol sodium solution until reaction liquid turned pink that could last for 30 s.

α-tocopherol Extraction and Measurement

α-tocopherol assay was conducted according to the method of Wang et al.^[23] Two g powder of fresh pulp were stirred in 5 mL of 90% (v/v) ethanol for 10 min, then 5 mL absolute ethyl alcohol was added for extraction 30 min, assisted by ultrasonic wave. The homogenates were centrifuged at 10,000 × g for 15 min at 4°C. The supernatant was passed through a 0.22 μm PTFE membrane (Tianjin Jinteng Experiment Equipment Co., Ltd., China, the same below) with syringe filter and stored at –20°C. α-tocopherol content was determined at 280 nm by a high-performance liquid chromatograph (HPLC, LC-20A, SHIMADZU Inc., Japan, the same below) equipped with an auto sampler, an ultraviolet detector, and integration software. The column was 250 mm × 4.6 mm i.d., 5 μm ZORBAX SB-C₁₈ (PerkinElmer Inc., USA, the same below). The mobile phase consisted of 95% absolute methanol in deionized water (v/v). The flow rate was 1 mL min⁻¹. The injection volume was 10 μL. DL-all-rac-α-tocopherol was used as the reference substance for standard curve. The concentration of α-tocopherol was calculated according to regression equation.

Carotenoid Extraction and Measurement

Determination of total carotenoid was carried out following the method described by Tao et al.^[24] One g powder of fresh pulp was mixed with 8 mL acetone containing 0.01% (w/v) butylated hydroxytoluene (BHT) and shaken for reaction at room temperature in the dark for 4 h; The mixture was centrifuged at 5000 × g for 10 min at room temperature. The supernatant was scanned at 470 nm, 645 nm, and 662 nm, and the absorbances were recorded respectively. The control sample consisting of water and reagents was used as a reference. Total carotenoid was calculated according to the formulas: Ca = 11.75A₆₆₂−2.35A₆₄₅, Cb = 18.61A₆₄₅−3.96A₆₆₂, Cxc = (1000A₄₇₀−2.27Ca-81.4Cb)/227. “A” means optical density (OD) value; Ca, Cb, and Cxc mean the concentrations of chlorophyll A, chlorophyll B, and total carotenoid, respectively.

Polyphenol Extraction and Measurement

Total polyphenol content was analyzed as described by Singleton et al.^[25] with modifications. Four g powder of fresh pulp was mixed with 10 mL of 70% (v/v) ethanol, incubated in a thermostatic water bath at 50°C for 5 min, and then filtered. The remaining residue was extracted again following the above procedure. The combined 70% (v/v) ethanol filtrates were centrifuged at 10,000 × g for 10 min at 4°C. After reaction at 85°C in the dark for 2 h,^[26] aliquots of 0.1 mL supernatant were added with 3 mL Folin-Ciocalteu reagent (the original binding was diluted 1:9 (v/v) with deionized water before use.) and 10% (w/v) Na₂CO₃ solution (3 mL). The OD values were measured at wavelength 760 nm by UV-Visible spectrophotometer; a blank sample consisting of water and reagents was used as a reference. Gallic acid reagent was used as reference substance for standard curve. The results were expressed as mg gallic acid equivalents (GAE) 100 g⁻¹ fresh weight (FW).

Flavonoid Extraction and Measurement

Total flavonoid content was determined according to Dae-Ok Kima et al.^[27] with modifications. Two mL supernatant which came from the same extract for polyphenol measurement (see the above) was mixed with 1.2 mL of l5% (w/v) NaNO₂; 6 min later, added with 0.6 mL 10% (w/v) Al(NO₃)₃; 6 more min later, added with 2 mL 4%(w/v) NaOH for another reaction; the absorbance was tested at 510 nm by UV-Visible spectrophotometer. A blank sample consisting of water and reagents was used as a reference. Rutin reagent was used as the reference substance for standard curve. The results were expressed as mg rutin equivalents (RE) 100 g⁻¹ FW.

Mangiferin Extraction and Measurement

The method described by Huang et al.^[28] was used to determine mangiferin content. Five g powder of fresh pulp was homogenized in 5 mL absolute ethyl alcohol. Mangiferin extraction was assisted by ultrasonic wave for 50 min; subsequently the homogenates were centrifuged at 10,000 × g for 15 min at 4°C; supernatants were passed through a 0.22 μm PTFE membrane with syringe filter and stored at –20°C; mangiferin content was determined at 258 nm by a high-performance liquid chromatograph. Column ZORBAX SB-C₁₈, mobile phase 32:68(v/v) absolute methanol:0.1% (w/v) phosphoric acid, flow rate 1 mL min⁻¹, and injection volume 10 μL were the chromatographic conditions. Mangiferin (98%, Shanghai Tauto Biotech Co., Ltd., China) was used as the reference substance for standard curve. Concentration of mangiferin was calculated according to regression equation.

Antioxidant Capacity Measurement

Antioxidant capacity was measured according to Benzie and Strain^[29] with modifications. One g powder of fresh pulp were mixed with 3 mL deionized water and filtered. The remaining residue was extracted again following the same procedure. Combined filtrates were centrifuged at 10,000 × g for 10 min at 4°C. An aliquot of 0.4 mL supernate was mixed with 3.6 mL TPTZ working solution for reaction. The OD value was monitored at 593 nm. A blank sample consisting of water and reagents was used as a reference. A series of ferrous sulfate with known concentration was used to get standard curve. The results were expressed as mmol of ferrous sulfate 100 g⁻¹ FW.

Statistical Analysis

Data were analyzed by analysis of variance (ANOVA). Duncan’s New Multiple range Test (DNMRT) was performed to determine the significant difference between samples at the 5% probability level. Correlation analysis, PCA, and regression analysis were conducted with the SAS software (Version 9.0).

RESULTS AND DISCUSSION

Ascorbic Acid Content

Ascorbic acid contents of mango pulp were shown in Figure 1. They decreased in the order of Lippens > Yuexi No. 1 > Zihua > Keitt > Tainong No. 1 > Zillate > Renong No. 1 > Renong No. 2 > Zill > Guire No. 82 > Chunhuang. Lippens observably owned the highest ascorbic acid level of 33.81 ± 2.27 mg 100 g⁻¹ FW, which was close to its female parent, Haden (23.6˜38.8 mg 100 g⁻¹ FW, obtained elsewhere),^[12] and also comparable with the value 36.4 mg 100 g⁻¹ FW published by USDA National Nutrient Database. While Chunhuang contained the lowest content of 4.89 ± 0.52 mg 100 g⁻¹ FW, together with Renong No. 2, Zill and Guire No. 82 (6.68 ± 0.75, 6.41 ± 2.74, and 5.75 ± 0.86 mg 100 g⁻¹ FW, respectively) closed to it. Only for the first six cultivars, ascorbic acid contents obtained by titration here (9.45˜33.81 mg 100 g⁻¹ FW) were similar to the values obtained by spectrophotometry^[12] or by HPLC.^[17,30]

Figure 1 Ascorbic acid content in mango pulp. Different letters above each column indicate significantly differences according to Duncan’s multiple test at P < 0.05; bars indicate the standard errors (the same below).

α-tocopherol Content

One of the most typical chromatogram (Fig. 2b) showed that the signal of α-tocopherol of mango pulp occurred with the elution time about 5.9 min, which was identified with the control (Fig. 2a, concentration 50 mg L⁻¹). The α-tocopherol levels of pulp were given in Fig. 3, which was in the order of Renong No. 1 > Chunhuang > Zihua > Guire No. 82 > Zill > Zillate > Lippens > Tainong No. 1 > Yuexi No. 1 > Renong No. 2 > Keitt. The mean of α-tocopherol content was 1.73 mg 100 g⁻¹ FW, which was equal to the value of Kheosawoei mango variety (1.40 mg 100 g⁻¹) from previous study by Charoensiri et al.^[31] while nearly twice of the value (0.9 mg 100 g⁻¹) from USDA National Nutrient Database. Interestingly, Renong No. 1 (provenance Australia cv. Sensation × cv. Kensinton pride) showed a fantastic sharp peak of 9.24 ± 0.45 mg 100 g⁻¹ FW, outdistancing others (Fig. 3); far from Renong No. 1, the second high value belonged to Chunhuang (2.61 ± 0.10 mg 100 g⁻¹ FW), being also significantly higher than that of cultivars ranging behind it; while Keitt was the lowest α-tocopherol (0.31 ± 0.05 mg 100 g⁻¹ FW); Zill and Zillate (Keitt’s off-spring) owned the similar α-tocopherol levels.

Figure 2 HPLC (A₂₈₀, nm) separation of α-tocopherol: (a) α-tocopherol chromatogram of standard sample and (b) α-tocopherol chromatogram of pulp extract.

Figure 3 α-Tocopherol content in mango pulp.

Total Carotenoid Content

The order of total carotenoid contents was Lippens > Yuexi No. 1 > Zill > Chunhuang > Tainong No. 1 > Zillate > Renong No. 2 > Zihua > Renong No. 1 > Guire No. 82 > Keitt (Fig. 4). Carotenoid contents of Lippens and Yuexi No. 1 (2.64 ± 0.13 and 2.60 ± 0.02 mg 100 g⁻¹ FW), were significantly higher than that of the others. USDA data showed that β-carotene was the richest carotenoid component in mango edible portion. Charoensiri et al.^[31] also reported that cv. Kheosawoei (unripe), Nahmdawgmai (ripe) and Rad (unripe) contained β-carotene of 34.5 ± 8.1, 308 ± 55.6, and 21.2 ± 5.6 μg 100 g⁻¹, respectively, suggesting that the riper the mango is, the higher β-carotene content it contains. It was noted that the highest carotenoid content owned by Lippens was even higher than that of its female parent, Haden;^[17] while Keitt was the lowest one.

Figure 4 Total carotenoid content in mango pulp.

Total Polyphenol Content

Polyphenols are known as the largest group of mango antioxidants. Saleh et al.^[15] and Ribeiro et al.^[14] found that polyphenol level was lower in pulp than that in the peel and seed kernel. Besides, the quantification of mango polyphenols by liquid chromatograph/mass spectrometer (LC-MS) had been reported in detail by Berardini et al.^[32] and Schieber et al.^[33] However, the data on total polyphenol content of more mango cultivars are still unknown.

In this study, the contents of total polyphenol were significantly different among the cultivars. The order as follows: Guire No. 82 > Yuexi No. 1 > Zihua > Lippens > Tainong No. 1 > Chunhuang > Zill > Keitt > Zillate > Renong No. 1 > Renong No. 2, which ranged from 141.36 ± 1.76 to 18.62 ± 5.22 mg of GAE 100 g⁻¹ FW (Fig. 5). Here we could find that total polyphenol content of Lippens corresponded to that of its female parent, Haden, picked in January from Peru.^[12] It was estimated that the intake of polyphenols in human daily diet was 0.15˜1.00 g per day,^[17] so mango fruit might availably contribute to antioxidant intake in human diet, especially Guire No. 82, who has the highest total polyphenol content.

Figure 5 Total polyphenol content in mango pulp; GAE: gallic acid equvalents.

Total Flavonoid Content

Flavonoid is one group of the polyphenol compounds, with the same biological functions as polyphenols. Total flavonoid levels of the tested mango cultivars were in the order of Guire No. 82 > Yuexi No. 1 > Zillate > Zihua > Tainong No. 1 > Lippens > Keitt > Chunhuang > Renong No. 2 > Zill > Renong No. 1 (Fig. 6), which was similar to the trend of total polyphenol content. The average content (1.27 mg of RE 100 g⁻¹ FW) of all cultivars was a little lower than the value from USDA database (2.00 mg of RE 100 g⁻¹ FW), but much lower than 12.18 mg of RE 100 g⁻¹ FW by HPLC elsewhere.^[34]

Figure 6 Total flavonoid content in mango pulp; RE : rutin equivalents.

Mangiferin Content

The same as flavonoid, mangiferin also belongs to polyphenols. According to Ribeiro et al.,^[14] mangiferin was present in the pulp, kernel, and peel of the mango cv. Haden, Tommy, Atkins, and Uba′, whereas it could not be detected in the pulp of cv. Palmer. The following chromatograms of mangiferin detection (Fig. 7) showed that the mangiferin signal of sample occurred with elution time 8.6 min, approximately identifying with the control (Fig. 7a, concentration 25 mg L⁻¹). Mangiferin levels of the 11 mango cultivars were given in Figure 8, which were in the order of Zillate > Guire No. 82 > Tainong No. 1 > Zill > Renong No. 1 > Renong No. 2 > Zihua > Yuexi No. 1 > Chunhuang > Keitt > Lippens, ranging from 0.15 ± 0.011 to 0.04 ± 0.004 mg 100 g⁻¹ FW. Deng et al.^[35] found that Guire No. 82 leaves held the highest mangiferin level among their selected cultivars. Likewise, here Guire No. 82 and Zillate, took the top value in pulp mangiferin level among the cultivars selected. While Zihua, Yuexi No. 1, Chunhuang and Keitt showed lower contents (0.06 ± 0.005, 0.05 ± 0.001, 0.04 ± 0.001, and 0.04 ± 0.002 mg 100 g⁻¹ FW, respectively), and no significant differences were observed among themselves.

Table 1  Antioxidant indexes of three cultivar types

Cultivar type	In vitro total antioxidant capacity (mmol FeSO4/100 g FW)	Ascorbic Acid (mg /100 g FW)	α-tocopherol (mg /100 g FW)	Total polyphenol (mg of GAE/100 g FW)	Flavonoids (mg of RE/100 g FW)	Mangiferin (mg /100 g FW)	Carotenoids (mg /100 g FW)
Red peel	0.22 a	12.90 a	0.74 a	45.34 b	1.09 a	0.08 a	1.85 a
Green peel	0.42 a	19.25 a	1.02 a	110.81 a	1.73 a	0.08 a	1.84 a
Yellow peel	0.30 a	10.19 a	4.18 a	51.36 b	1.04 a	0.09 a	1.88 a

Data of each group were shown as the average of three cultivars.

Figure 7 HPLC (A₂₅₈, nm) separation of mangiferin: (a) mangiferin chromatogram of standard and (b) mangiferin chromatogram of pulp extract.

Figure 8 Mangiferin content in mango pulp.

Table 2  Correlation analysis of the indexes

Indexes	In vitro total antioxidant capacity	Ascorbic acid	α-tocopherol	Total polyphenol	Flavonoids	Mangiferin	Carotenoids
In vitro total antioxidant capacity	1.00000	0.20481	−0.18696	0.86892**	0.69562*	0.16158	0.2593
Ascorbic acid	------	1.00000	−0.27678	0.24983	−0.02374	−0.57363	0.29963
α-tocopherol	------	------	1.00000	−0.24745	−0.28078	−0.02551	−0.18102
Total polyphenols	------	------	------	1.00000	0.83789*	0.12389	0.15869
Flavonoids	------	------	------	------	1.00000	0.40542	−0.1063
Mangiferin	------	------	------	------	------	1.00000	−0.15109
Carotenoids	------	------	------	------	------	------	1.00000

means negative correlation; — means none.

**Indicates significant correlation (P < 0.01).

*Indicates appreciable correlation (P < 0.05).

Total In vitro Antioxidant Capacity

The total in vitro antioxidant capacity was observed in the order of Guire No. 82 > Lippens > Tainong No. 1 > Yuexi No. 1 > Chunhuang > Zihua > Zill > Keitt > Zillate > Renong No. 1 > Renong No. 2 (Fig. 9). Here, the trend of in vitro antioxidant capacity was also similar to that of the total polyphenol. As was reported by Manthey and Perkins-Veazie,^[12] there were the uniform changes in total phenolic content and DPPH antioxidant capacity, relative to cultivar type. The results confirmed that the variation of total phenolic contents and the variation of total in vitro antioxidant capacities were in close agreement with each other.

Figure 9 The FRAP value of mango pulp.

Antioxidants and Total In vitro Antioxidant Capacities of Cultivars with Different Peel Color

By dividing all cultivars into three groups, i.e., red, green, and yellow peel cultivars, the data of each parameter was analyzed. Unexpectedly, there were no statistically significant differences in any indexes among the three groups, except for total polyphenol, which was three times higher in the green peel group than that in the red peel group (Table 1). It probably suggested that neither a few antioxidants nor total in vitro antioxidant capacity of mango pulp was dependent on peel color.

Correlation Analysis and Principal Component Regression Analysis

The result of Correlation Analysis (Table 2) indicated that there was a highly significant positive correlation between the content of total polyphenol and in vitro total antioxidant capacity; significant positive correlations were also found between the flavonoid content and in vitro total antioxidant capacity, and between flavonoid level and polyphenol level.

The obtained results of principal component regression analysis were presented in Table 3. Regression analysis was further performed to obtain the regression equation, i.e., Y = 0.96674 * (0.081427 Z₁ − 0.348094 Z₂ + 0.109860 Z₃ + 0.244058 Z₄ + 0.625268 Z₅ + 0.640005 Z₆), R² = 0.9346. The results indicated that all of the antioxidants presented positive correlations to total in vitro antioxidant capacity at varying degrees, except α-tocopherol. Moreover, both total polyphenol and total flavonoid levels had the same variation trends and played key roles in total in vitro antioxidant capacity. It was harmoniously closed to the report from Matsusaka and Kawabata^[36] that radical scavenging abilities were closely correlated with total polyphenol content in fruits.

Table 3  Eigenvectors (the princomp procedure, SAS system)

Index	Prin 1	Prin 2	Prin 3	Prin 4	Prin 5	Prin 6
Carotenoids (Z1)	0.081427	0.416148	0.706274	0.534878	−0.091552	0.163987
α-tocopherol (Z2)	−0.348094	−0.249369	−0.403601	0.782331	0.181543	0.093546
Ascorbic acid (Z3)	0.109860	0.639291	−0.271047	−0.060097	0.704144	0.079630
Mangiferin (Z4)	0.244058	−0.565124	0.416430	0.009386	0.652698	−0.146810
Total polyphenols (Z5)	0.625268	0.088680	−0.225763	0.306559	−0.164727	−0.655052
Flavonoids (Z6)	0.640005	−0.169449	−0.201083	0.064690	−0.098446	0.712300

CONCLUSIONS

According to the above statements, it was concluded that (a) there were diversities in antioxidant contents and in vitro antioxidant capacities among cultivars and among groups, e.g., Guire No. 82 had superior polyphenol content, flavonoid level, and in vitro antioxidant capacity, while the highest level of α-tocopherol was observed in Renong No. 1; (b) higher contents of ascorbic acid, total polyphenol, total flavonoid, and total in vitro antioxidant capability were observed in green peel mangoes than that in red peel or yellow peel mangoes; (c) correlation analysis and principal component regression analysis demonstrated that positive correlations exist among the measured antioxidants and total in vitro antioxidant capability, except α-tocopherol. Besides, polyphenol chemicals were deemed to be one group of the most critical factors affecting on total in vitro antioxidant capability. Meanwhile, the strong synchronism of total polyphenol and flavonoid contents in pulp were found.

ACKNOWLEDGEMENTS

This work was supported by Forestry Science & Technology Pillar Program (2006BAD01A1705), State-level Public Welfare Basic Scientific Research Operation Cost (SSCRI200909), and National Natural Science Foundation of China (No. 31101535). The authors wish to thank South Subtropical Crops Research Institute (SSCRI), China Academy of Tropical Agricultural Sciences (CATAS) for facilities support to this study.