Variations of peel essential oils during fruit ripening in four lemon (Citrus limon (L.) Burm. F.) cultivars

Abstract

BACKGROUND: Lemon processing procedures yield a significant amount of waste as peels, which are 57% of processed lemons and represent a possible source of bioactive compounds (essential oils, EOs). EOs were extracted from lemon fruits belonging to four cultivars harvested at four different sampling times (25 October, 23 November, 20 December, 1 February), characterized, and quantified through gas chromatography-mass spectrometry. RESULTS: The chemical composition of EOs highlighted that 26 compounds of the four lemon cultivars at the different ripening stages were clearly identified. The compounds analysed belonged to four chemical classes: monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes, and fatty alcohol esters. Among the monoterpene hydrocarbons, D-limonene,-pinene, and -terpinene were the most abundant; and among the oxygenated monoterpenes, -terpineol, nerol, and geraniol were the most abundant. Quantitative gas chromatography-mass spectrometry analysis of the most abundant monoterpene hydrocarbons ( -pinene, -pinene, myrcene, D-limonene, and -terpinene) highlighted that the amount of EOs decreased during ripening stages. 'Ovale di Sorrento' and 'Sfusato Amalfitano' showed the highest level of EOs in December, whereas in 'Femminello Cerza' and 'Femminello Adamo' this occurred in November. EOs, as well as the phenolic compounds, were positively correlated with the antioxidant activity (2,2 ′ -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid). CONCLUSIONS: EOs reached the highest level in the four lemon cultivars at different ripening stages. Campanian cultivars ('Ovale di Sorrento' and 'Sfusato Amalfitano') showed the greatest EO content in November, whereas in Sicilian cultivars ('Femminello Cerza' and 'Femminello Adamo') this occurred in December. Besides phenolic compounds, measured in lemon peel extracts, EOs can contribute to antioxidant activity, as demonstrated by the positive correlation. Composition and quantification of EOs Chemical composition of EOs during ripening stagesThe chemical composition of extracted EOs was analysed during ripening stages (Table 2). A total of 26 compounds were clearly identified in the fruit peel extracts of the four cultivars and at different ripening stages. Significant variations among cultivars and ripening stages were observed.The compounds analysed were assigned to four chemical classes: monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes, and fatty alcohol esters. Monoterpene hydrocarbons were the dominant fraction of EOs, with an average relative abundance of 94.5%. During the ripening they decreased from 95.2% to 93.3%, and among them the compounds represented most were D-

Untargeted Metabolomics of Rind Essential Oils Allowed to Differentiate Two Closely Related Clementine Varieties

“…Some of these studies reported a limonene decrease in EO at the end of harvest time [8,23], which was not observed in this study. The decrease in the abundance of monoterpene hydrocarbons along Citrus ripening could be explained by the high unsaturation level of these compounds that would make them more unstable to factors such as light or chemical oxidation [23]. In addition, Wang and Liu (2014) reported in C. reticulata an increase of sesquiterpene hydrocarbons at the end of the harvesting period [8], although this effect was not observed in our study.…”

“…Nevertheless, no differences were detected for most compounds including limonene. The lower accumulation of several monoterpene hydrocarbons at the end of harvest time had also been reported in other Citrus EO, like C. reticulata, C. aurantium and C. limon [8,22,23]. Some of these studies reported a limonene decrease in EO at the end of harvest time [8,23], which was not observed in this study.…”

“…The lower accumulation of several monoterpene hydrocarbons at the end of harvest time had also been reported in other Citrus EO, like C. reticulata, C. aurantium and C. limon [8,22,23]. Some of these studies reported a limonene decrease in EO at the end of harvest time [8,23], which was not observed in this study. The decrease in the abundance of monoterpene hydrocarbons along Citrus ripening could be explained by the high unsaturation level of these compounds that would make them more unstable to factors such as light or chemical oxidation [23].…”

Utilization of Plantago major seed mucilage containing Citrus limon essential oil as an edible coating to improve shelf‐life of buffalo meat under refrigeration conditions

“…(2012), five different classes of phenolic compounds are found in Citrus species: flavanone (such as O‐dihexoside of naringenin), flavones (such as luteolin‐6‐C‐glucoside, apigenin‐7‐O‐rutinoside‐4′‐O‐glucoside, apigenin‐6‐C‐hexoside‐O‐hexoside, luteolin‐7‐O‐neohesperidoside‐4′‐O‐glucoside, and aligenin‐8‐C‐hexoside‐O‐acylrhamnoside), flavonols (such as 7‐O‐rutinosides of isorhamnetin, kaempferol, quercetin, and tamarixetin, isorhamnetin‐3‐O‐rutinoside‐7‐O‐glucoside, kaempferol‐3‐O‐rutinoside, and tamarixetin‐3‐O‐rutinoside‐7‐O‐glucoside), hydroxycinnamic acids (such as O‐hexoside of sinapic and ferulic acids), and coumarins (such as O‐rhamnosylhexoside and O‐hexoside of scopoletin). The high contents of phenolic compounds have been found in citrus species essential oils and extracts (Di Rauso Simeone et al., 2020; Hojjati & Barzegar, 2017; Sultana et al., 2015). The phenolic compounds act as electron donors in free radical reactions and are often correlated to the antioxidant effect of the essential oils.…”

Lemon Oils Attenuate the Pathogenicity of Pseudomonas aeruginosa by Quorum Sensing Inhibition

“…The main CEO components are classified into terpenes (monoterpenes and sesquiterpenes), alcohols, aldehydes and esters [ 4 ]. In Citrus limon essential oils, the most abundant monoterpene hydrocarbons reported are d -limonene, γ -terpinene and β -pinene and between oxygenated monoterpenes, the most abundant are α -terpineol, nerol and geraniol [ 10 ]. Quantitatively, limonene is the main compound of C. limon essential oils at levels typically ranging between 70 and 48% [ 8 ].…”