Isolation and structure elucidation of avocado seed (Persea americana) lipid derivatives that inhibit Clostridium sporogenes endospore germination

Chemistry and Bioactivity of the Genus Persea - A Review

This review provides the first comprehensive appraisal of bioactive compounds and their biological activities in Persea species from 1950 to 2023. Relevant articles from reputable databases, including PubMed, Web of Science, Science Direct and Google Scholar were collected, leading to the isolation of about 141 metabolite compounds, mainly flavonoids, terpenoids, fatty alcohols, lignoids, and γ-lactone derivatives. These compounds exhibit diverse biological activities, including insecticidal, antifeedant, nematicidal, antibacterial, antifungal, antiviral, cytotoxic, anti-inflammatory, and antioxidant properties. The review emphasizes the significant chemical and pharmacological potential of different Persea species, encouraging further research in various fields and medicine. Valuable insights into potential applications of Persea plants are provided.

Enzymatic, Antioxidant, and Antimicrobial Activities of Bioactive Compounds from Avocado (Persea americana L.) Seeds

The aim of this research was to identify and quantify biologically active compounds from avocado (Persea americana L.) seeds (AS) utilizing different techniques with the use of ultrasound (US), ethanol (EtOH), and supercritical carbon dioxide (scCO₂) for possible applications in (bio)medicine, pharmaceutical, cosmetic, or other relevant industries. Initially, a study of the process efficiency (η) was carried out, which revealed yields in the range of 2.96-12.11 wt%. The sample obtained using scCO₂ was found to be the richest in total phenols (TPC) and total proteins (PC), while the sample obtained with the use of EtOH resulted in the highest content of proanthocyanidins (PAC). Phytochemical screening of AS samples, quantified by the HPLC method, indicated the presence of 14 specific phenolic compounds. In addition, the activity of the selected enzymes (cellulase, lipase, peroxidase, polyphenol oxidase, protease, transglutaminase, and superoxide dismutase) was quantified for the first time in the samples from AS. Using DPPH radical scavenging activity, the highest antioxidant potential (67.49%) was detected in the sample obtained with EtOH. The antimicrobial activity was studied using disc diffusion method against 15 microorganisms. Additionally, for the first time, the antimicrobial effectiveness of AS extract was quantified by determination of microbial growth-inhibition rates (MGIRs) at different concentrations of AS extract against three strains of Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas fluorescens) bacteria, three strains of Gram-positive (Bacillus cereus, Staphylococcus aureus, and Streptococcus pyogenes) bacteria, and fungi (Candida albicans). MGIRs and minimal inhibitory concentration (MIC₉₀) values were determined after 8 and 24 h of incubation, thus enabling the screening of antimicrobial efficacy for possible further applications of AS extracts as antimicrobial agents in (bio)medicine, pharmaceutical, cosmetic, or other industries. For example, the lowest MIC₉₀ value was determined for B. cereus after 8 h of incubation in the case of UE and SFE extracts (70 μg/mL), indicating an outstanding result and the potential of AS extracts, as the MIC values for B. cereus have not been investigated so far.

The Enigmatic Aliphatic Acetogenins and Their Correlations With Lipids During Seed Germination and Leaf Development of Avocado (Persea americana Mill.)

Lipids in avocados have been widely studied due to their nutritional value and several reported bioactivities. Aliphatic acetogenins are a relevant component of the avocado lipidome and have been tested for several potential food and pharma industries applications. This work followed the evolution of avocado fatty acids (FAs) and aliphatic acetogenins during seed germination and leaf growth. Oil extracts of embryonic axes, cotyledons, and leaves from seedlings and trees were divided to analyze free acetylated acetogenins (AcO-acetogenins), and free FAs. Embryonic axes from germinating seeds contained the highest amount of AcO-acetogenins and FAs; this tissue also accumulated the most diverse FA profile with up to 22 detected moieties. Leaves presented the highest variations in AcO-acetogenin profiles during development, although leaves from seedlings accumulated the simplest FA profile with only 10 different FAs. Remarkably, AcO-acetogenins represented half of the carbons allocated to lipids in grown leaves, while embryonic axes and cotyledons always contained more carbons within FAs during germination. Thus, we hypothesized the use of the AcO-acetogenin acyl chain for energy production toward β-oxidation. Also, α-linolenic and docosahexaenoic acids (DHAs) were proposed as close AcO-acetogenin intermediaries based on a correlation network generated using all these data. Another part of the oil extract was fractionated into different lipid classes before transesterification to profile FAs and acetogenins bound to lipids. Acetogenin backbones were identified for the first time in triglycerides from cotyledons and mainly in polar lipids (which include phospholipids) in all developing avocado tissues analyzed. Seed tissues accumulated preferentially polar lipids during germination, while triglycerides were consumed in cotyledons. Seedling leaves contained minute amounts of triglycerides, and polar lipids increased as they developed. Results from this work suggest acetogenins might be part of the energy and signaling metabolisms, and possibly of membrane structures, underlining the yet to establish role(s) of these unusual lipids in the avocado plant physiology.

Avocado seeds (Persea americana cv. Criollo sp.): Lipophilic compounds profile and biological activities

This study aimed to evaluate the volatile or lipophilic chemical profiling and the biological activities of avocado (Persea americana cv. Criollo sp.) seed extracts. Chemical profile of volatile compounds (GC/MS), antioxidant properties (phenolic compounds, DPPH radical scavenging activities and reducing power), and antimicrobial activity (Salmonella Typhimurium and Staphylococcus aureus) of avocado (Persea americana cv. Criollo sp.) seed extracts (ethanol and acetone) were characterized. Sixteen volatile chemical compounds were determined, including isoprenoid derivatives (estragole), esters of fatty acids (linoleic and linolenic acids), and their derivatives (9,12-Octadecadien-1-ol and 9,12,15-Octadecatrien-1-ol). Acetone was the best solvent to obtain volatile compounds from avocado seed; this extract also showed a higher reducing power (56.35 mg AAE/100 g). Maximum S. aureus and S. Typhimurium log reductions were 4.0 ± 0.3 and 1.8 ± 0.3 at the highest amount used (2000 mg/L), without significant effect (p < 0.05) of the solvent used. According to the results of the volatile chemical profiling of avocado (Persea americana cv. Criollo sp.) seed extracts, they can have potential application as antioxidant (212.75 and 183.75 mg Trolox/100 g) and antimicrobial additives.

Acyl-Acyl Carrier Protein Desaturases and Plant Biotic Interactions

Interactions between land plants and other organisms such as pathogens, pollinators, or symbionts usually involve a variety of specialized effectors participating in complex cross-talks between organisms. Fatty acids and their lipid derivatives play important roles in these biological interactions. While the transcriptional regulation of genes encoding acyl–acyl carrier protein (ACP) desaturases appears to be largely responsive to biotic stress, the different monounsaturated fatty acids produced by these enzymes were shown to take active part in plant biotic interactions and were assigned with specific functions intrinsically linked to the position of the carbon–carbon double bond within their acyl chain. For example, oleic acid, an omega-9 monounsaturated fatty acid produced by Δ⁹-stearoyl–ACP desaturases, participates in signal transduction pathways affecting plant immunity against pathogen infection. Myristoleic acid, an omega-5 monounsaturated fatty acid produced by Δ⁹-myristoyl–ACP desaturases, serves as a precursor for the biosynthesis of omega-5 anacardic acids that are active biocides against pests. Finally, different types of monounsaturated fatty acids synthesized in the labellum of orchids are used for the production of a variety of alkenes participating in the chemistry of sexual deception, hence favoring plant pollination by hymenopterans.

Avocado fruit and by-products as potential sources of bioactive compounds

The increased demand for avocado, and therefore production and consumption, generate large quantities of by-products such as seeds, peel, and defatted pulp, which account for approximately 30% of fruit weight, and which are commonly discarded and wasted. The present review focuses on various compounds present in avocado fruit and its by-products, with particular interest to those that can be potentially used in different industrial forms, such as nutraceuticals, to add to or to formulate functional foods, among other uses. Main molecular families of bioactive compounds present in avocado include phenolic compounds (such as hydroxycinnamic acids, hydroxybenzoic acids, flavonoids and proanthocyanins), acetogenins, phytosterols, carotenoids and alkaloids. Types, contents, and possible functions of these bioactive compounds are described from a chemical, biological, and functional approach. The use of avocado and its by-products requires using processing methods that allow highest yield with the least amount of unusable residues, while also preserving the integrity of bioactive compounds of interest. Avocado cultivar, fruit development, ripening stage, and processing methods are some of the main factors that influence the type and amount of extractable molecules. The phytochemical diversity of avocado fruit and its by-products make them potential sources of nutraceutical compounds, from which functional foods can be obtained, as well as other applications in food, health, pigment, and material sectors, among others.

Characterization of a New Antienterovirus D68 Compound Purified from Avocado

One of the major challenges in development of antienterovirus (EV) drugs is in the safety of the drug. Here, we attempted to identify anti-EV compounds from an edible plant extract library and found potent antienterovirus D68 (EV-D68) activity in avocado (Persea americana). The purified identity is determined as 2R,4R-(12Z,15Z)-heneicosa-12,15-diene-1,2,4-triol, named avoenin. Avoenin shows an EC₅₀ of 2.0 μM for EV-D68 (Fermon) infection with CC₅₀ of >150 μM in RD cells by targeting the uncoating step of EV-D68 infection. Resistant mutations of EV-D68 (VP3-V24I, S173P, and S180G) to avoenin confer cross-resistance to pleconaril, an uncoating inhibitor of EV-D68. The inhibitory effect of avoenin is substantially specific to EV-D68 among the EVs. This work reveals avoenin as the identity of anti-EV-D68 activity in avocado and offers insights into development of a novel and effective strategy to overcome EV-D68 infection and its related respiratory diseases.

Chemical Profile and Safety Assessment of a Food-Grade Acetogenin-Enriched Antimicrobial Extract from Avocado Seed

Acetogenins are bioactive fatty acid derivatives found in avocado tissues. Their efficacy as antimicrobials has been documented and initiated interest to use them as replacements of synthetic food additives. The present work focused on evaluation of multiple analytical methodologies for detection and quantification of organic solids present in a food-grade acetogenin-enriched extract (Avosafe®), and on its safety evaluations using bacterial reverse mutation (AMES) tests and acute oral toxicity to rat assays. Results confirmed chemical structures of two acetogenins as present in Avosafe® (AcO-avocadyne-(0) and AcO-avocadiene B-(3)), and together with seven other previously known compounds, quantified 94.74 ± 5.77% w/w of its solids as acetogenins. Safety evaluations indicated that Avosafe® was non-mutagenic and had an acute median lethal oral dose (LD50) to rats higher than the maximum concentration tested (>2000 mg·kg-1), with no signs of macroscopic abnormalities in organs. Mean body weight and hematological and biochemical parameters were normal after 14 days of a single oral dose of 2000 mg·kg-1. The results advance scientific information on the safety of avocado seed acetogenins and also generate new knowledge on profiles and concentrations of individual acetogenins found in avocado tissues (seed, pulp, and leaves) and in Avosafe®.

Production of d-Lactate from Avocado Seed Hydrolysates by Metabolically Engineered Escherichia coli JU15

Agroindustry residues can be used to produce valuable chemicals such as lactic acid, which is a primary chemical platform with many industrial applications. Biotechnological processes are the main approach of lactic acid production; however, culture media has an important impact on their costs. As a result, researchers are exploring various methods of production that use residual or waste biomass as raw materials, most of which are rich in lignocellulose. Nevertheless, starch and micronutrients such as those contained in avocado seeds stand out as promising feedstock for the bioprocess as well. In this study, the lactogenic Escherichia coli strain JU15 was evaluated for producing d-lactate using an avocado seed hydrolysate medium in a controlled stirred-tank bioreactor. The highest lactic acid concentration achieved was 37.8 g L−1 using 120 g L−1 as the content of initial reducing sugars. The results showed that d-lactate can be produced from avocado seed, which hydrolysates to 0.52 g L−1 h−1 using the engineered E. coli JU15. This study may serve as a starting point to further develop bioprocesses for producing metabolites using avocado seed hydrolysates.

Analytical Method To Detect and Quantify Avocatin B in Hass Avocado Seed and Pulp Matter

Avocatin B, an avocado-derived compound mixture, was demonstrated recently to possess potent anticancer activity by selectively targeting and eliminating leukemia stem cells. Avocatin B is a mixture of avocadene and avocadyne, two 17-carbon polyhydroxylated fatty alcohols (PFAs), first discovered in avocado seeds; their quantities in avocado pulp are unknown. Analytical methods to detect avocado seed PFAs have utilized NMR spectroscopy and GC-MS; both of these lack quantitative capacity and accuracy. Herein, we report a sensitive LC-MS method for the quantitation of avocadene and avocadyne in avocado seed and pulp. The method has a reliable and linear response range of 0.1-50 μM (0.03-17.2 ng/μL) for both avocadene and avocadyne ( r² > 0.990) with a lower limit of quantitation (LLOQ) of 0.1 μM. The intra- and interassay accuracy and precision of the quality control (QC) samples at LLOQ showed ≤18.2% percentage error and ≤14.4% coefficient of variation (CV). The intra- and interassay accuracy and precision for QC samples at low and high concentrations were well below 10% error and CV. This method was successfully applied to quantify avocadene and avocadyne in total lipid extracts of Hass avocado pulp and seed matter.

Avocado fruit maturation and ripening: dynamics of aliphatic acetogenins and lipidomic profiles from mesocarp, idioblasts and seed

BACKGROUND

Avocado fruit contains aliphatic acetogenins (oft-acetylated, odd-chain fatty alcohols) with promising bioactivities for both medical and food industries. However, we have scarce knowledge about their metabolism. The present work aimed to study changes in acetogenin profiles from mesocarp, lipid-containing idioblasts, and seeds from 'Hass' cultivar during fruit development, germination, and three harvesting years. An untargeted LC-MS based lipidomic analysis was also conducted to profile the lipidome of avocado fruit in each tissue.

RESULTS

The targeted analysis showed that acetogenin profiles and contents remained unchanged in avocado mesocarp during maturation and postharvest ripening, germination, and different harvesting years. However, a shift in the acetogenin profile distribution, accompanied with a sharp increase in concentration, was observed in seed during early maturation. Untargeted lipidomics showed that this shift was accompanied with remodeling of glycerolipids: TAGs and DAGs decreased during fruit growing in seed. Remarkably, the majority of the lipidome in mature seed was composed by acetogenins; we suggest that this tissue is able to synthesize them independently from mesocarp. On the other hand, lipid-containing idioblasts accumulated almost the entire acetogenin pool measured in the whole mesocarp, while only having 4% of the total fatty acids. The lipidome of this cell type changed the most when the fruit was ripening after harvesting, TAGs decreased while odd-chain DAGs increased. Notably, idioblast lipidome was more diverse than that from mesocarp.

CONCLUSIONS

Evidence shown here suggests that idioblasts are the main site of acetogenin biosynthesis in avocado mesocarp. This work unveiled the prevalence of aliphatic acetogenins in the avocado fruit lipidome and evidenced TAGs as initial donors of the acetogenin backbones in its biosynthesis. It also sets evidence for acetogenins being included in future works aimed at characterizing the avocado seed, as they are a main component of their lipidome.

Inhibitory Activity of Avocado Seed Fatty Acid Derivatives (Acetogenins) Against Listeria Monocytogenes

High standards regarding Listeria monocytogenes control and consumer demands for food products without synthetic additives represent a challenge to food industry. We determined the antilisterial properties of an enriched acetogenin extract (EAE) from avocado seed, compared it to two commercial antimicrobials (one enriched in avocado acetogenins), and tested purified molecules. Acetogenin composition in pulp and seed of Hass avocado was quantified. EAE were obtained by two sequential centrifuge partition chromatography separations and molecules purified by preparative chromatography and quantified by HPLC-MS-TOF and HPLC-PDA. Avocado seed extracts which are the following two: 1) EAE and 2) the commercially available antimicrobial Avosafe®, presented similar inhibition zones and chemical profiles. Minimum inhibitory concentration (MIC) values of extracts and two isolated acetogenins varied between 7.8 and 15.6 mg/L, were effective at 37 and 4 °C, and showed a bactericidal effect probably caused by increased membrane permeability and lytic effects, evidenced by flow cytometry at 10 and 100× MIC. Activity was comparable to Mirenat®. Most potent acetogenins were Persenone C (5) and A (6), and AcO-avocadenyne (1), the latter exclusively present in seed. Common features of bioactive molecules were the acetyl moiety and multiple unsaturations (2 to 3) in the aliphatic chain, some persenones also featured a trans-enone group. Seeds contained 1.6 times higher levels of acetogenins than pulp (5048.1 ± 575.5 and 3107.0 ± 207.2 mg/kg fresh weight, respectively), and total content in pulp was 199 to 398 times higher than MIC values. Therefore, acetogenin levels potentially consumed by humans are higher than inhibitory concentrations. Results document properties of avocado seed acetogenins as natural antilisterial food additives.

Avocado Proanthocyanidins as a Source of Tyrosinase Inhibitors: Structure Characterization, Inhibitory Activity, and Mechanism

Proanthocyanidins were purified from avocado (Persea americana) fruit, and their structures were analyzed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and high-performance liquid chromatography-electrospray ionization-QTRAP mass spectrometry (HPLC-ESI-QTRAP MS) techniques. The results obtained from mass spectrometry (MS) analysis demonstrated that the proanthocyanidins were homo- and heteropolymers of procyanidins, prodelphinidins, propelargonidins, and procyanidin gallate. From the enzyme analysis, the results showed that they could inhibit the monophenolase and diphenolase activities of tyrosinase. The inhibition mechanism of the proanthocyanidins on the enzyme was further studied, and the results indicated that they were reversible and competitive inhibitors. Finally, the results acquired from molecular docking, fluorescence quenching, and copper ion interacting tests revealed that adjacent hydroxyl groups on the B ring of proanthocyanidins could chelate the dicopper catalytic center of the enzyme. In addtion, proanthocyanidins were proven to be an efficient quencher of substrates. This study would lay a scientific foundation for their use in agriculture, food, and nutrition industries.

A targeted metabolomics approach to characterize acetogenin profiles in avocado fruit (Persea americana Mill.)

Lauraceous acetogenins are fatty acid derivatives with an odd-carbon aliphatic chain found in avocado (Persea americana Mill.).

Isolation and chemical identification of lipid derivatives from avocado (Persea americana) pulp with antiplatelet and antithrombotic activities

Bioassay-guided isolation of acetogenins from avocado pulp within vitroantiplatelet aggregation andin vivoantithrombotic effects in CD1 mice.

Activity-guided identification of acetogenins as novel lipophilic antioxidants present in avocado pulp (Persea americana)

Avocado fruit is a rich source of health-related lipophilic phytochemicals such as monounsaturated fatty acids, tocopherols, carotenes, acetogenins and sterols. However, limited information is available on the contribution of specific phytochemicals to the overall antioxidant capacity (AOC) of the fruit. Centrifugal partition chromatography was used as fractionation tool, guided by an in vitro chemical assay of oxygen radical absorbance capacity (ORAC). Subsequent experiments focused on isolation and characterization of the chemical nature of the main contributors to lipophilic AOC of avocado pulp. ORAC values obtained for acetogenins were contrasted with results from an isolated kidney mitochondria membrane lipid peroxidation bioassay. The present study established that lipophilic AOC of the pulp was significantly higher than its hydrophilic AOC. Our results confirmed the presence of acetogenins in the fractions with highest lipophilic AOC, and for the first time linked them as contributors to lipophilic-ORAC values. Further HPLC-PDA/MS-TOF analysis led to structural elucidation of two novel acetogenins, not previously reported as present in avocado pulp, along with five already known related-compounds. Antioxidant properties observed for avocado pulp acetogenins by the ORAC assay suggested that, in the presence of an emulsifying agent, acetogenins could serve as novel lipophilic antioxidants in a food matrix. Results from isolated mitochondria lipid peroxidation bioassay, indicated that L-ORAC values which may have relevance for food matrix applications, should not be interpreted to have a direct relevance in health-related claims, compounds need to be evaluated considering the complexity of biological systems.