Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds
In the process of longan production and processing, a large amount of remnants is produced, such as dried longan pericarps and seeds, which have been reported to be rich in polyphenols but not effectively utilized. In this paper, the total phenolic contents in the remnants of longan pericarps and se...
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MDPI AG
2023-01-01
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| Online Access: | https://www.mdpi.com/2223-7747/12/3/512 |
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| author | Mengli Wang Ting Chen Qin Wang Yan Shi |
| author_facet | Mengli Wang Ting Chen Qin Wang Yan Shi |
| author_sort | Mengli Wang |
| collection | DOAJ |
| description | In the process of longan production and processing, a large amount of remnants is produced, such as dried longan pericarps and seeds, which have been reported to be rich in polyphenols but not effectively utilized. In this paper, the total phenolic contents in the remnants of longan pericarps and seeds were found to be 39.58 ± 3.54 and 69.53 ± 1.99 mg/g (DW), respectively, accounting for 60–80% of those in fresh samples. The contents of extractable condensed tannins (ECTs) in the remnants of longan pericarps and seeds were 19.25 ± 6.71 mg/g (DW) and 44.59 ± 2.05 mg/g (DW), respectively, accounting for 60–70% of the fresh samples. These data indicate that the polyphenols in the remnants of the sampled longan pericarps and seeds were effectively retained. The antioxidant capacity of ECTs from the longan pericarps and seeds was more than 60% of the fresh samples measured with the 1, 1-diphenyl-2-trinitrophenylhydrazine and ferric reducing ability of plasma methods. Further exploration showed that ECTs from the longan pericarps and seeds had significant inhibitory effects on <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, <i>Salmonella</i> and <i>Staphylococcus aureus</i>. The minimum inhibitory concentration (MIC) of the longan pericarp ECTs on all four studied bacteria was 3 mg/mL. The MIC of longan seed ECTs on Salmonella was 3 mg/mL, and that of the other three bacteria was 1.5 mg/mL. In view of the good antioxidant and antibacterial activities of longan pericarps and seeds, we applied them to the preservation of fresh-cut lotus roots. When the concentration of ECTs in the longan pericarps and seeds was 2 mg/mL and 1 mg/mL, respectively, the two kinds of ECTs showed an obvious preservative effect. After the ECT treatment of the lotus roots, their browning degree was reduced, their color was better maintained, their respiration was inhibited and their nutrient loss was reduced. Bacterial reproduction was inhibited, and cell senescence was slowed. Accordingly, the shelf life of ECT-treated fruits and vegetables can be effectively extended. Overall, we can suggest that ECTs from the remnants of dried longan pericarps and seeds could be used as natural preservatives for fresh-cut fruits and vegetables. |
| first_indexed | 2024-03-11T09:29:02Z |
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| language | English |
| last_indexed | 2024-03-11T09:29:02Z |
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| spelling | doaj.art-06da88922dc14135a92eed1c97b43e1d2023-11-16T17:43:26ZengMDPI AGPlants2223-77472023-01-0112351210.3390/plants12030512Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and SeedsMengli Wang0Ting Chen1Qin Wang2Yan Shi3School of Life Sciences, Xiamen University, Xiamen 361102, ChinaSchool of Life Sciences, Xiamen University, Xiamen 361102, ChinaSchool of Life Sciences, Xiamen University, Xiamen 361102, ChinaSchool of Life Sciences, Xiamen University, Xiamen 361102, ChinaIn the process of longan production and processing, a large amount of remnants is produced, such as dried longan pericarps and seeds, which have been reported to be rich in polyphenols but not effectively utilized. In this paper, the total phenolic contents in the remnants of longan pericarps and seeds were found to be 39.58 ± 3.54 and 69.53 ± 1.99 mg/g (DW), respectively, accounting for 60–80% of those in fresh samples. The contents of extractable condensed tannins (ECTs) in the remnants of longan pericarps and seeds were 19.25 ± 6.71 mg/g (DW) and 44.59 ± 2.05 mg/g (DW), respectively, accounting for 60–70% of the fresh samples. These data indicate that the polyphenols in the remnants of the sampled longan pericarps and seeds were effectively retained. The antioxidant capacity of ECTs from the longan pericarps and seeds was more than 60% of the fresh samples measured with the 1, 1-diphenyl-2-trinitrophenylhydrazine and ferric reducing ability of plasma methods. Further exploration showed that ECTs from the longan pericarps and seeds had significant inhibitory effects on <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, <i>Salmonella</i> and <i>Staphylococcus aureus</i>. The minimum inhibitory concentration (MIC) of the longan pericarp ECTs on all four studied bacteria was 3 mg/mL. The MIC of longan seed ECTs on Salmonella was 3 mg/mL, and that of the other three bacteria was 1.5 mg/mL. In view of the good antioxidant and antibacterial activities of longan pericarps and seeds, we applied them to the preservation of fresh-cut lotus roots. When the concentration of ECTs in the longan pericarps and seeds was 2 mg/mL and 1 mg/mL, respectively, the two kinds of ECTs showed an obvious preservative effect. After the ECT treatment of the lotus roots, their browning degree was reduced, their color was better maintained, their respiration was inhibited and their nutrient loss was reduced. Bacterial reproduction was inhibited, and cell senescence was slowed. Accordingly, the shelf life of ECT-treated fruits and vegetables can be effectively extended. Overall, we can suggest that ECTs from the remnants of dried longan pericarps and seeds could be used as natural preservatives for fresh-cut fruits and vegetables.https://www.mdpi.com/2223-7747/12/3/512longan pericarp and seedextractable condensed tanninsantioxidant capacityfood preservationfresh-cut lotus roots |
| spellingShingle | Mengli Wang Ting Chen Qin Wang Yan Shi Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds Plants longan pericarp and seed extractable condensed tannins antioxidant capacity food preservation fresh-cut lotus roots |
| title | Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds |
| title_full | Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds |
| title_fullStr | Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds |
| title_full_unstemmed | Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds |
| title_short | Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds |
| title_sort | antioxidant bacteriostatic and preservative effects of extractable condensed tannins isolated from longan pericarps and seeds |
| topic | longan pericarp and seed extractable condensed tannins antioxidant capacity food preservation fresh-cut lotus roots |
| url | https://www.mdpi.com/2223-7747/12/3/512 |
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