Efficiency and selectivity of triterpene acid extraction from decoctions and tinctures prepared from apple peels

Extraction of Ursolic Acid from Apple Peel with Hydrophobic Deep Eutectic Solvents: Comparison between Response Surface Methodology and Artificial Neural Networks

Extracting ursolic acid (UA) from plant resources using organic solvents is incompatible with food applications. To address this, in this study, 15 edible hydrophobic deep eutectic solvents (HDESs) were prepared to extract UA from apple peel, the extraction conditions were optimized, and the optimization strategies were compared. It was found that the solubility of UA in the HDESs can be 9 times higher than the traditional solvent such as ethanol. The response surface optimization concluded that temperature had the greatest effect on the extraction and the optimized test conditions obtained as follows: temperature of 49 °C, time of 32 min, solid-liquid ratio of 1:16.5 g/mL, respectively. Comparing the response surface methodology (RSM) and artificial neural networks (ANN), it was concluded that ANN has more accurate prediction ability than RSM. Overall, the HDESs are more effective and environmentally friendly than conventional organic solvents to extract UA. The results of this study will facilitate the further exploration of HDES in various food and pharmaceutical applications.

Triterpene Content in Flesh and Peel of Apples Grown on Different Rootstocks

Advancements in rootstock breeding and selection have revolutionized the manner in which apples are grown throughout the world. Fruit tree breeding has typically focused on key horticultural characteristics. Even though agents with health benefits have been investigated more frequently during the recent years, information about the effect of different cultivation factors, such as the rootstock, on triterpene concentration is still lacking. The present study aimed to evaluate triterpene profiles and the quantitative composition of different parts of apple fruit that was grown on 17 various origin and vigor rootstocks. HPLC analyses of triterpenes in apple samples were performed. The highest total content of triterpenes (7.72 ± 0.39 mg/g) was found in peel samples of apples grown on the dwarf rootstock 62-396-B10^®. Depending on the rootstock, apple peel samples accumulated 3.52 to 4.74 times more triterpene compounds than apple flesh samples. Ursolic acid was the predominant triterpene compound in apple peel and flesh samples. The highest content of ursolic acid (5.84 ± 0.29 mg/g) was found in peel samples of apples grown on the dwarf rootstock 62-396-B10^®. Meanwhile, the lowest amount of ursolic acid (3.25 ± 0.16 mg/g) was found in apple peel samples grown on the dwarf rootstock Cepiland-Pajam^®2. A proper match of a cultivar and a rootstock can program a fruit tree to grow larger amounts of higher quality, antioxidant-rich, and high-nutrition-value fruit.

Phenolic Content and Antioxidant Activity in Apples of the ‘Galaval’ Cultivar Grown on 17 Different Rootstocks

Apple cultivars are one of the main factors setting the composition of bioactive compounds in apples and the quality of the fruit. However, research has been providing increasing amounts of data on the influence of rootstocks on the variations in the composition of bioactive compounds in apples. The aim of the study was to determine the influence of rootstocks on the changes in the qualitative and quantitative composition of phenolic compounds and their antioxidant activity in vitro in apple flesh and peel. HPLC analyses of phenolic compounds in apple samples were performed. The rootstock–scion combination had a significant effect on the composition and antioxidant activity of phenolic compounds in apple samples. Depending on the rootstock, the total content of phenolic compounds in apple flesh of the ‘Galaval’ cultivar could vary by 2.9 times, and in the peel by up to 90%. The genotype of the rootstock resulted in the highest variation in total flavan-3-ol content in apple flesh—by as much as 4.3 times—while the total content of flavonols varied by 2.1 times. In apple peel, on the contrary, the greatest variation was recorded for the total flavonol content (by 4.4 times), and the total flavan-3-ol content varied the least (by 1.8 times). A proper match of a cultivar and a rootstock can program a fruit tree to grow larger amounts of higher-quality, antioxidant-rich, and high-nutrition-value fruit.

Antioxidant, Anti-Inflammatory, and Cytotoxic Activity of Extracts from Some Commercial Apple Cultivars in Two Colorectal and Glioblastoma Human Cell Lines

Cancer initiation and development are closely related to oxidative stress and chronic inflammation. The aim of this study was to evaluate apple extracts and individual tritepenes antioxidant, anti-inflammatory, and cytotoxic activities. Dry extracts of apple were analyzed by HPLC-PDA. A hyaluronidase inhibition assay was selected to determine the anti-inflammatory effect. Cytotoxic activities against human colon adenocarcinoma cell line (HT-29) and human glioblastoma cell line (U-87) were determined using MTT, cell colony formation, and spheroid growth assays. Radical scavenging and reducing activities were evaluated using DPPH, ABTS, FRAP, and CUPRAC assays, respectively. The apple extracts inhibited hyaluronidase from 26.38 ± 4.4% to 35.05 ± 3.8%. The AAW extract possessed the strongest cytotoxic activity (EC₅₀ varied from 113.3 ± 11.11 µg/mL to 119.7 ± 4.0 µg/mL). The AEW extract had four and five times stronger antiradical activity when determined by ABTS and DPPH, and two and eight times stronger reducing activity when evaluated by CUPRAC and FRAP, respectively. Understanding the mechanisms of apple extracts and individual triterpenes as hyaluronidase inhibitors and antioxidants related in cancer development may be a benefit to future study in vivo, as well as cancer prognosis or the development of new, innovative food supplements, which could be used for chronic disease prevention.

Variation of Triterpenes in Apples Stored in a Controlled Atmosphere

Apples are seasonal fruits, and thus after harvesting apples of optimal picking maturity, it is important to prepare them properly for storage and to ensure proper storage conditions in order to minimize changes in the chemical composition and commercial quality of the apples. We studied the quantitative composition of triterpenic compounds in the whole apple, apple peel and apple flesh samples before placing them in the controlled atmosphere (CA) chambers, and at the end of the experiment, 8 months later. HPLC analysis showed that highest total amount of triterpenic compounds (1.99 ± 0.01 mg g^-1) was found in the whole apple samples of the 'Spartan' cultivar stored under variant VIII (O₂-20%, CO₂-3%, N₂-77%) conditions. Meanwhile, the highest amount of triterpenic compounds (11.66 ± 0.72 mg g^-1) was determined in the apple peel samples of the 'Auksis' cultivar stored under variant II (O₂-5%, CO₂-1%, N₂-94%) conditions. In the apple peel samples of the 'Auksis' cultivar stored under variant I (O₂-21%, CO₂-0.03%, N₂-78.97%) conditions, the amount of individual triterpenic compounds (ursolic, oleanolic, corosolic, and betulinic acids) significantly decreased compared with amount determined before the storage. Therefore, in the apple flesh samples determined triterpenic compounds are less stable during the storage under controlled atmosphere conditions compared with triterpenic compounds determined in the whole apple and apple peel samples.

Extraction of High Value Triterpenic Acids from Eucalyptus globulus Biomass Using Hydrophobic Deep Eutectic Solvents

Triterpenic acids (TTAs), known for their promising biological properties, can be found in different biomass sources and related by-products, such as Eucalyptus globulus bark, and have been extracted using organic volatile solvents such as dichloromethane. Recently, deep eutectic solvents (DES) have been identified as promising alternatives for the extraction of value-added compounds from biomass. In the present work, several hydrophobic DES were tested for the extraction of TTAs from E. globulus bark. Initial solubility studies revealed that DES based on menthol and thymol as the most promising solvents for these compounds given the highest solubilities obtained for ursolic acid (UA) at temperatures ranging from room temperature up to 90 °C. Accordingly, an eutectic mixture of menthol:thymol (1:2) was confirmed as the best candidate for the TTAs extraction from E. globulus outer bark, leading to extraction yields (weight of TTA per weight of biomass) at room temperature of 1.8 wt% for ursolic acid, 0.84 wt% for oleanolic acid and 0.30 wt% for betulinic acid. These values are significantly higher than those obtained with conventional organic solvents under similar conditions. The results obtained using these DES are promising for the recovery of TTAs for nutraceutical and pharmacological applications, while reinforcing the potential of DES as promising solvents to be applied in biorefinery processes.

Valorization of olive tree leaves: Extraction of oleanolic acid using aqueous solutions of surface-active ionic liquids

The global olive oil industry annually generates approximately 750,000-1,500,000 tons of Olea europaea leaves as waste that are typically burned for energy production. Yet, this agricultural by-product is a rich source of oleanolic acid, a high value triterpenic acid with outstanding pharmaceutical and nutraceutical activities. The present study focuses on the extraction of oleanolic acid from dried O. europaea leaves using aqueous solutions of surface-active ionic liquids as alternative solvents. A number of imidazolium-based ionic liquids with variable chain length, different anions and optional side-chain functionalization was synthesized and employed in the extraction of oleanolic acid. Ionic liquids with long alkyl chains remarkably enhance the solubility of oleanolic acid in water, thus being able to compete with the solubilities afforded by molecular organic solvents, such as chloroform. Consequently, they are suitable alternatives for the solid-liquid extraction of triterpenic acids from natural matrices and provide improved extraction yields of up to 2.5 wt% oleanolic acid extracted from olive tree leaves.

Aqueous solutions of surface-active ionic liquids: remarkable alternative solvents to improve the solubility of triterpenic acids and their extraction from biomass

Triterpenic acids (TTAs) are well known for their relevant biological properties and have been facing an increasing interest for nutraceutical and pharmaceutical applications. To overcome the concerns associated to the commonly used volatile organic solvents for their extraction from biomass, here we investigate the potential of aqueous solutions of ionic liquids (ILs) as alternative solvents. The solubility of ursolic acid (UA) was firstly determined in several aqueous solutions of ILs (hydrotropes or surface-active) at 30°C to appraise the dissolution phenomenon. Conventional surfactants were also investigated for comparison purposes. The collected data reveal a remarkable enhancement in the solubility of UA (8 orders of magnitude) in surface-active ILs aqueous solutions when compared to pure water. Afterwards, the potential of these ILs aqueous solutions was confirmed by their use in the extraction of TTAs from apple peels. Total extractions yield of TTAs of 2.62 wt.% were obtained using aqueous solutions of surface-active ILs at moderate conditions, overwhelming the extraction yields of 2.48 wt.% obtained with chloroform and 1.37 wt.% with acetone using similar conditions.

Selective and cost-effective protocol to separate bioactive triterpene acids from plant matrices using alkalinized ethanol: Application to leaves of Myrtaceae species

Background:

Triterpenes as betulinic (BA), oleanolic (OA) and ursolic acids (UA) have increasingly gained therapeutic relevance due to their wide scope of pharmacological activities. To fit large-scale demands, exploitable sources of these compounds have to be found and simple, cost-effective methods to extract them developed. Leaf material represents the best plant sustainable raw material. To obtain triterpene acid-rich extracts from leaves of Eugenia, Psidium and Syzygium species (Myrtaceae) by directly treating the dry plant material with alkalinized hydrated ethanol. This procedure was adapted from earlier methods to effect depolymerization of the leaf cutin.

Materials and Methods:

Extracts were prepared by shaking the milled dry leaves in freshly prepared 2% NaOH in 95% EtOH solution (1:4 w/v) at room temperature for 6 h. Working up the product in acidic aqueous medium led to clear precipitates in which BA, OA and UA were quantified by gas chromatography.

Results:

Pigment-free and low-polyphenol content extracts (1.2–2.8%) containing 6–50% of total triterpene acids were obtained for the six species assayed. UA (7–20%) predominated in most extracts, but BA preponderated in Eugenia florida (39%). Carried out in parallel, n-hexane defatted leaves led to up to 9% enhancement of total acids in the extracts. The hydroalcoholate treatment of Myrtaceae species dry leaves proved to be a cost-effective and environmentally friendly method to obtain triterpene acids, providing them be resistant to alkaline medium. These combined techniques might be applicable to other plant species and tissues.