Green Extraction Techniques for Obtaining Bioactive Compounds from Mandarin Peel (Citrus unshiu var. Kuno): Phytochemical Analysis and Process Optimization

Abstract

In this study, an efficient utilization and valorization of mandarin peel (Citrus unshiu Marc. var. Kuno) was investigated using innovative and green extraction techniques. The first step of this study included the extraction and analysis of the volatile compounds by performing a supercritical CO2 (SC-CO2) extraction under different operating pressure conditions (100 and 300 bar). The analysis of volatile compounds of the obtained extracts was conducted by gas chromatography-mass spectrometry (GC-MS), and limonene was found to be the dominant volatile component (13.16% at 100 bar; 30.65% at 300 bar). After SC-CO2 treatment, the exhausted citrus peel waste enriched with bioactive compounds was subjected to subcritical water extraction (SWE) in a wide temperature range (130–220 °C) using different solvent-solid ratio (10–30 mL/g) in time periods from 5 to 15 min, in order to obtain bioflavonoids. Identification and quantification of present bioflavonoids was conducted by high-performance liquid chromatography with a with a diode array detector (HPLC), and hesperidin (0.16–15.07 mg/g) was determined as the most abundant flavanon in mandarin peel with other polyphenolic compounds that were possible by-products of thermal degradation. At higher temperatures, the presence of 5-hydroxymethylfurfural (5-HMF) and chlorogenic acid were detected. Antiradical activity and total phenolic content in the extracts were determined using spectrophotometric methods, while the process optimization was performed by response surface methodology (RSM).

Bioactive compounds extracted by liquid and supercritical carbon dioxide from citrus peels

“…Furthermore, terpinene, linalool, terpineol, decanal, perillaldehyde, carvacrol, caryophyllene and cadinene according to Šafranko et al . (2021), farnesene according to Xiong & Chen (2020) and 1,1‐dimethoxyoctane were also identified.…”

Variation in Compositions and Biological Activities of Essential Oils from Four Citrus Species: Citrus limon, Citrus sinensis, Citrus paradisi, and Citrus reticulata

“…The EOs of C. limon comprises D‐limonene, γ‐terpinene, α‐pinene, β‐pinene, and many other compounds [11] . The content of this EO is also affected by many factors, such as variety, harvest year, fruit maturity, and the extraction system [12–16] . α‐Pinene plays a role in the inhibition of caspase‐3, which is related to cell apoptosis and therefore has anticancer effects [17] .…”

Optimization of MAE for the Separation of Nicotine and Phenolics from Tobacco Waste by Using the Response Surface Methodology Approach

“…Identification and quantification of phenolic compounds (CCA, NCA, CA, rutin and nicotiflorin) was performed using previously reported gradient method [ 38 ] with separation obtained on a: COSMOSIL 5C18-MS-11 (4.6 × 250 mm, 5 µm) chromatographic column (Agilent, Santa Clara, CA, USA) and using methanol and 1% acetic acid solution in Milli-Q water (conductivity ≤ 0.054 μS/cm) as a mobile phase.…”