Abstract
Phalaenopsis (Phal.) orchids including white, yellow, and purple flowers are some of the most important commercial orchids worldwide. These flowering plants can be considered to be promising sources of antioxidants since several medicinal orchids were shown to have potential antioxidant activities. The antioxidant activities and several secondary metabolite compounds of the methanolic extracts of four parts (the root, pedicel, leaf, and flower) of three hybrids of white (Phal. ‘City More’), yellow (Phal. ‘Sogo Meili’), and purple (Phal. ‘Queen Beer’) flowering orchids were investigated. Results showed that the highest levels of chlorophyll a and chlorophyll b were respectively obtained in leaf extracts of white and purple orchids, whereas carotenoid showed the highest content in the flower extract of the yellow orchid. Among all tested extracts, flavonoids and anthocyanin demonstrated the highest levels in the flower extract of the purple orchid, whereas the highest level of polyphenols was observed in the flower extract of the yellow orchid. The leaf extract of the white orchid was the most effective extract with a 50% inhibitory concentration in the DPPH-scavenging activity assay, while the highest ferrous iron-chelating effect was observed in flower extracts of the yellow orchid and purple orchid, and the pedicel extract of the purple orchid. In the reducing power assay, the flower extract of the white orchid showed the most potent extract, followed by the leaf extract of the yellow orchid and the flower extract of the purple orchid. Relationships between flower colors and antioxidant activities of these orchids showed them to be potential sources of antioxidants for both medicinal use and stress-tolerance in these orchids.
Highlights
The autoxidation process and oxidative stresses cause various problems in human health, such as ageing, cancer, diabetes, and cardiovascular diseases (Sikora et al, 2008; Huang et al, 2016)
Results show that in all orchid species tested, levels of Chl a, Chl b, total Chl, and carotenoids in leaves were significantly higher than those of other plant parts in each plant, while the flowers contained a higher ratio of Chl a/b compared to other parts due to the Chl b lower contents
Among all examined samples, the highest flavonoid and anthocyanin contents were found in the flower extract of the purple orchid at 138.70 ± 3.03 mg QE.g-1 DW and 147.48 ± 11.85 μg.g-1 DW, respectively
Summary
The autoxidation process and oxidative stresses cause various problems in human health, such as ageing, cancer, diabetes, and cardiovascular diseases (Sikora et al, 2008; Huang et al, 2016). The use of plant products as natural antioxidants in reducing free radical-induced tissue injury has attracted much attention in recent years (Pokorný, 2007; Brewer, 2011). These natural antioxidants have been widely proven to be potential medicines to maintain health, prevent oxidative stress-mediated diseases, and delay ageing processes (Djeridane et al, 2006; Beta et al, 2017; Caleja et al, 2017). The search for new and safe antioxidants from natural sources is the objective of continued investigations
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