Phytochemical composition and in vitro antioxidant activities ofCitrus sinensispeel extracts

Abstract

BackgroundCitrus sinensis peels are usually discarded as wastes; however, they are rich sources of Vitamin C, fibre, and many nutrients, including phenolics and flavonoids which are also good antioxidant agents. This study aimed to examine phytochemical composition and antioxidant capabilities of C. sinensis peel extracted conventionally with different methanol/water, ethanol/water, and acetone/water solvents.MethodsC. sinensis peels were subjected to extraction with 100%, 70% and 50% of methanol, ethanol, and acetone, respectively, as well as hot water extraction. Antioxidant activities of the peel extracts were examined via the 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity, ferric reducing antioxidant power (FRAP) assay, and oxygen radical absorbance capacity (ORAC) assay. Total phenolic content and total flavonoid content of the extracts were measured via the Folin-Ciocalteau method and the aluminium chloride colorimetric method, respectively. Phenolic acid and organic acid composition of the peel extracts were further determined via high performance liquid chromatography (HPLC) while flavonoid content was identified via ultra performance liquid chromatography (UPLC).ResultsDPPH radical scavenging activity of C. sinensis peel extracts varied from 8.35 to 18.20 mg TE/g, FRAP ranged from 95.00 to 296.61 mmol Fe(II)/g, while ORAC value ranged from 0.31 to 0.92 mol TE/g. Significant level of association between the assays was observed especially between TPC and FRAP (R-square = 0.95, P < 0.0001). TPC of various C. sinensis peel extracts ranged from 12.08 to 38.24 mg GAE/g, with 70% acetone/water extract (AEC) showing the highest TPC. TFC ranged from 1.90 to 5.51 mg CE/g. Extraction yield ranged from 0.33 to 0.54 g/g DW and tended to increase with increasing water concentration in the solvent. In the phytochemical investigation, five phenolic acids were identified using HPLC, including gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, caffeic acid and ferulic acid. A total of five organic acids including lactic acid, citric acid, L-mallic acid, kojic acid and ascorbic acid were quantified via HPLC. In addition, concentrations of six flavonoids including catechin, epigallocatechin, vitexin, rutin, luteolin and apigenin were determined via UPLC.Discussion and ConclusionPhytochemicals including phenolics and flavonoids in C. sinensis peel extracts exhibited good antioxidant properties. Among the extracts, 70% AEC with highest TPC and high TFC content showed greatest antioxidant activity in all three assays. Different phenolic acids, organic acids and flavonoids were also identified from the extracts. This study indicated that C. sinensis peels contained potential antioxidant compounds which could be exploited as value added products in the food industry.

Anti-inflammatory and antioxidant potential, in vivo toxicity, and polyphenolic composition of Eugenia selloi B.D.Jacks. (pitangatuba), a Brazilian native fruit

“…Our findings showed that the peroxyl radical scavenging capacity of F3 was three-fold greater than that of Ese. A previous study testing gallic acid showed ORAC values of 7.88 mol TE/g, which is 32-fold and 12-fold more potent than that of Ese and F3, respectively [37]. Here, isomers of quercetin were identified in both samples and were previously shown to have antioxidant activity against peroxyl radical [38].…”

Quality, Bioactive Compounds and Antioxidant Activity During Maturation of Oranges Produced in the Borborema Territory

“…According to Ferreira, Silva and Nunes (2018), the high antioxidant activity of citrus peel extracts may be explained by their phenolic composition, such as hesperidin, naringin, rutin, and caffeic and chlorogenic acids. As mentioned by Bilgiçli, Aktaş and Levent (2014);and Liew et al (2018), the bioactive phytochemicals present in the citrus peel can be exploited for various applications, such as the extraction of natural antioxidants, food additives and dyes for the food industry. These antioxidants act to protect against the accumulation of reactive oxygen species, eliminating them from the system through irreversible dehydrogenation.…”

“…The albedo of 'Mimo-do-Céu' had a comparatively lower EC 50 value (1700.74 g pulp g DPPH -1 ) and, consequently, higher antioxidant activity at the C3 stage. From literature studies, the residues of the citrus agroindustry contained TAA values of 11035 μM TE g -1 (BARBOSA; RUVIARO; MACEDO, 2018), and 9188 μM TE g -1 (MADEIRA JR; MACEDO, 2015) whereas, in citrus peels, the DPPH • radical scavenging activity ranged from 8.35 to 18.20 mg TE g -1 (LIEW et al, 2018), depending on the extraction technique. These differences may be a result of the different analytical protocols of the extraction method, production region, cultivar and maturation stage (FERREIRA; SILVA; NUNES, 2018).…”

“…As Zou et al (2016) stated, pre-/postharvest and processing factors influence the chemical structure and antioxidant capacity of citrus fruits. This activity further depends on the composition of the extract, as well as on the conditions and mechanisms of the test used (LIEW et al, 2018).…”

Peer Review #1 of "Antioxidant activity, α-glucosidase inhibition and phytochemical profiling of Hyophorbe lagenicaulis leaf extracts (v0.1)"

“…The reduction in absorbance was used to assess the antioxidant potential (Prieto et al, 1999). The antioxidant potential of plant extracts is directly proportional to the concentration and quality of phytochemicals including phenolics and flavonoids (Liew et al, 2018). The high α-glucosidase inhibitory action of 60% ethanolic extract was probably due to its high phenolic and flavonoid contents.…”