Extraction and Analysis of Plant Active Ingredients

The extraction of active ingredients from vegetable matter is one of the most attractive research fields in the literature. An objective that promotes this large interest is the possibility of identifying eco-friendly and innovative processes, active products, and materials. However, care must be taken in selecting processes and extraction conditions to minimize the co-extraction of undesired compounds. The analysis of the composition of the extracted compounds by chromatography, mass spectrometry, and related techniques is a relevant step in determining the performance of the extraction process and the purity of the extracted compounds in order to use them for pharmaceutical applications.

This Special Issue includes 10 research papers, 1 communication, and 1 review, and reports innovative extraction techniques and advanced analytical methods used for the recovery of high-added-value compounds from vegetable matter.

In particular, Rehman et al. [1] studied the bronchodilator effect of Achillea fragrantissima essential oil (AFO) in guinea pigs’ tracheas and the influence of drying on the quantity and composition of AFO using GC-MS and GC analyses. These authors found that AFO induced a strong relaxation to counteract the effects of carbachol (CCh) and showed bronchodilator effects predominantly due to anticholinergic and K⁺ channel activation followed by weak Ca⁺⁺ channels inhibition.

El Mansouri et al. [2] investigated the adsorption behavior of Eriochrome Black T (EBT) on waste hemp activated carbon (WHAC). The surface of the WHAC was modified by H₃PO₄ acid treatment. They concluded that the adsorption mechanism followed pseudo-second-order kinetics and the maximum removal of EBT by WHAC was in the range of 44–62% at pH 7, using an adsorbent dose of 10–70 mg, a contact time of 3 h, and an initial dye concentration of 10 mg L⁻¹.

Althurwi et al. [3] compared essential oils (EOs) prepared from the fresh and dried stems of Commiphora gileadensis. Although the components were quite similar, the amount of oil decreased from about 2.20 to 1.80% upon drying. The topical application of the Commiphora gileadensis chloroform extract promoted wound healing in rats.

Abdel-Kader et al. [4] designed a reverse-phase high-performance thin-layer chromatography (RP-HPTLC) protocol for the simultaneous determination of bioactive sesquiterpene coumarins feselol and samarcandin in the methanol extract of five Ferula species. The results indicated that F. drudeana contained the highest abundance of the more active samarcandin, whereas F. duranii had the largest quantity of the less active feselol.

In another work, Abdel-Kader et al. [5] developed and applied an HPTLC method that can simultaneously and effectively detect and quantify curcumin I, curcumin II, and curcumin III in fresh, dry rhizomes of Curcuma longa and in an herbal formulation of C. longa extracts.

Scognamiglio et al. [6] highlighted that supercritical fluid extraction coupled with fractional separation can represent a suitable alternative to isolate cuticular waxes from vegetable matter that preserves their natural properties and composition, without contamination with organic solvent residues. Operating in this way, they can be considered as a fingerprint of the vegetable matter, where C₂₇, C₂₉, and C₃₁ were the most abundant compounds.

Zou et al. [7] developed a UHPLC-ESI-QTOF-MS/MS method to be an efficient strategy to annotate bioactive compounds, to reveal the difference in bioactive components of Morus spp. leaves, and to provide important information for the high-value production of Morus cultivars in the food and supplement fields.

Wang and Li [8] proposed an environmentally friendly method for the extraction of seven active coumarins from Angelica dahurica (Hoffm.) Benth. & Hook.f. ex Franch. & Sav. (A. dahurica) based on deep eutectic solvents (DESs). The DES system using a molar ratio of choline chloride, citric acid, and water of 1:1:2 showed the best extraction effect whereas the optimal extraction conditions were a liquid/solid ratio of 10:1 (mL/g), extraction time of 50 min, extraction temperature of 59.85 °C, and moisture content of 49.28%.

Givonetti et al. [9] investigated the SDS-PAGE profile of hempseed proteins; They compared different methods of extraction, two conditions to maintain low temperatures during seed grinding, and two solubilization buffers. TCA/acetone, MTBE/methanol, and direct protein solubilization of defatted hempseed flour resulted in the highest protein content.

Ilyas et al. [10] evaluated the immunomodulatory activity of various fractions of Phyllanthus maderaspatensis, column eluents of the ethyl acetate fraction, and their polyphenols. They found that the ethyl acetate fraction contained a high amount of catechin, quercetin, ellagic acid kaempferol, and rutin, which are involved in immunomodulation.

Rajasree et al. [11] measured the antioxidant activity of a methanolic extract of Cucumis melo Linn (MECM). The results showed the presence of various phytochemical constituents, such as carbohydrates, alkaloids, sterols, phenolic compounds, terpenes, and flavonoids, and suggested that MECM may serve as a putative source of natural antioxidants for therapeutic and nutraceutical applications.

Chiriac et al. [12] summarized the current advances in the state of the art for polyphenol identification and quantification. In particular, analytical techniques ranging from high-pressure liquid chromatography to hyphenated spectrometric methods were discussed, and they highlighted that the elucidation of the compound’s structure is one of the most important steps for natural products research.