Antioxidants from plant sources have been an increasing concern to consumers since synthetic antioxidants such as butylated hydroxy toluene (BHT) have restricted usage in foods, due to carcinogenic activity [
The years 2011–2020 are recognized as the “Decade on Biodiversity” by the United Nations to promote the importance and utilization of underutilized foods. Recently, research and development activities on antioxidants from underutilized fruits have become a great priority [
2-2′-Azino-bis (3-ethylbenz-thiazoline-6-sulfonic acid (ABTS), 2, 4, 6-tri (2-pyridyl)-l, 3, 5-triazine (TPTZ), aluminium chloride, tween-20, linoleic acid, chlorogenic acid, protocatechuic acid, kaempferol, rutin, hydroxybenzoic acid, beta carotene, quercetin, gallic acid, BHT, trichloroacetic acid, thiobarbituric acid, sodium azide, tris-HCl buffer, phosphate buffer, and Hepes were obtained from Sigma-Aldrich Co. (MO, USA). Folin-Ciocalteu reagent, trifluoroacetic acid (HPLC Grade), acetonitrile (HPLC Grade), and hydrogen peroxide were obtained from Merck (Darmstadt, Germany). All other chemicals and solvents used were of analytical grade.
Whole bunch of unripe (Figure
Physical parameters of
Unripe | Ripe | |
---|---|---|
Whole fruit bunch | ||
Weight (kg) | 7.2 ± 0.19b | 16.1 ± 0.16a |
Length (cm) | 25.5 ± 2.5b | 34.5 ± 2.7a |
Perimeter (cm) | 81.2 ± 4.5b | 108.9 ± 6.3a |
Individual fruit | ||
Weight (g) | 138.1 ± 5b | 159.6 ± 7.7a |
Length (cm) | 11.1 ± 0.5b | 12.9 ± 0.7a |
Breadth (cm) | 7.8 ± 0.5 | 8.1 ± 0.3 |
Endosperm | ||
Weight (g) | 3.6 ± 1.5b | 19.6 ± 0.8a |
Length (cm) | 3.0 ± 0.2b | 4.5 ± 0.5a |
Perimeter (cm) | 5.8 ± 0.7b | 10.1 ± 0.5a |
For each treatment means in a row followed by different letters are significantly different at
Dry powder (10 g) from unripe and ripe endosperms of NF was extracted separately with 50% ethanol (100 mL) using an orbital shaker (Unimax 1010, Heidolph, Germany). The shaker was maintained at a speed of 400 rpm and the extraction was carried out at 30°C for 1 h duration. The extracts were then filtered using Whatman filter paper (no. 4), concentrated, freeze dried using bench top freeze dryer (Virtis, NY, USA), and stored at −20°C until further analysis.
Total phenolics content (TPC) of the extracts was determined according to the method developed by Singleton and Rossi [
Total flavonoid content (TFC) was measured using the aluminum chloride colorimetric assay described by Liu et al. [
Radical scavenging activity of the samples against ABTS was carried out according to the method described by Re et al. [
DPPH radical scavenging activities were determined based on a method developed by Prasad et al. [
Ferric reducing antioxidant power assay of the extracts was performed according to the method of Re et al. [
Beta carotene bleaching assay was performed according to the method of Velioglu et al. [
Antioxidant capacity by phosphomolybdenum method was determined by the method of Prieto et al. [
Individual phenolic compounds in EEU and EER of NF were identified using validated UHPLC method described by Kong et al. [
Data were expressed as means ± standard deviations (SD) of three determinations and analyzed by SPSS V.13 (SPSS Inc., Chicago, USA). One way analysis of variance (ANOVA) and Duncan’s multiple-range test were used to determine the differences among the means.
The fruit of NF was selected for the present investigation, since it is one of the important underutilized plants of Malaysia. Although the sap is often used as beverage [
Phenolics and flavonoids present in fruits and vegetables have received considerable attention due to their potential antioxidant activities [
Different antioxidant compounds could react through different mechanisms, and hence a single method alone cannot fully evaluate the antioxidant capacity of foods [
ABTS method is developed based on a decolorization technique. Once added, the antioxidant causes a reduction of ABTS, which could be measured at 734 nm. This assay is performed to measure the ability of antioxidants to inhibit radical cation induced by persulfate. Strong antioxidants have the ability to change the blue color of ABTS into light blue color. The change in absorbance is proportional to the antioxidant concentration [
ABTS radical scavenging activity of unripe and ripe endosperm extracts of
DPPH is a stable free radical and accepts an electron or hydrogen radical to become a stable diamagnetic molecule which is widely used to investigate radical scavenging activity. In DPPH radical scavenging assay, antioxidants react with DPPH and convert it to yellow coloured
DPPH radical scavenging activity of unripe and ripe endosperm extracts of
Ferric reducing antioxidant power is widely used in evaluating antioxidant activity of plant polyphenols. Principally, FRAP assay treats the antioxidants in the sample as reductant in a redox-linked colorimetric reaction [
FRAP values of unripe and ripe endosperm extracts of
Beta carotene bleaching method is widely used to measure antioxidant activity of plant extracts. It is an
Antioxidant activity coefficient values determined by beta carotene bleaching method of unripe and ripe endosperm extracts of
Antioxidant capacities of NF extracts were measured spectrophotometrically using phosphomolybdenum method, which is based on the reduction of Mo (IV) to Mo (V) by the sample analyte and subsequent formation of green phosphate/Mo (V) compounds with a maximum absorption at 695 nm [
Antioxidant capacity of unripe and ripe endosperm extracts of
HPLC chromatograms from EEU (Figure
Phenolic compound composition of unripe and ripe endosperm extracts of
Peak number | Compound | Retention time (min) |
|
Unripe | Ripe |
---|---|---|---|---|---|
1 | Gallic acid | 2.1 | 272 |
|
|
2 | Protocatechuic acid | 2.9 | 294 | 5.52 ± 0.40a | 3.88 ± 0.50b |
3 | Hydroxybenzoic acid | 3.9 | 256 | 1.10 ± 0.07a | 0.87 ± 0.06b |
4 | Chlorogenic acid | 6.1 | 326 | 14.5 ± 1.30a | 9.7 ± 1.10b |
5 | Rutin | 9.5 | 354 | 2.7 ± 0.04a | 2.2 ± 0.07b |
6 | Cinnamic acid | 10.7 | 272 |
|
|
7 | Quercetin | 11.6 | 372 |
|
|
8 | Kaempferol | 11.9 | 364 |
|
|
For each treatment means in a row followed by different letters are significantly different at
HPLC chromatogram of unripe (a) and ripe endosperm extract (b) of
Our results are in good agreement with Monde et al. [
Antioxidant activity and phenolic content of EEU determined in the present study were higher compared to EER. This is in good agreement with other researchers, where they had reported parallel results [
The total phenolics content of NF is higher when compared to acai palm (123.1 GAE/g) [
Unripe endosperm extract of
The authors have no conflict of interest to declare.
The financial support of Science-Fund from Ministry of Agriculture, Malaysia (02-02-10-SF0131 and 05-01-04-SF1137), is thankfully acknowledged. The authors would like to thank the assistance of laboratory staffs from the Department of Nutrition and Dietetic and the use of laboratories facilities of Universiti Putra Malaysia throughout the research project.