Natural Compounds in Plants, 2nd Volume

Tea polyphenols, the primary bioactive constituents responsible for the various health benefits of tea, can be categorized into different subgroups according to their structural characteristics. However, the distinctions in antiviral activity among the diverse types of polyphenolic compounds remain unexplored. In the present study, fifty-eight tea polyphenols with varied structures, including eleven undescribed compounds, were isolated from Rougui Wuyi rock tea. Their molecular structures were elucidated using comprehensive analytical approaches of NMR, HRMS, CD spectroscopic data and acid hydrolysis. The isolated polyphenol analogs could be structurally classified into two main categories: flavan-3-ols, which include catechins, flavoalkaloids, procyanidins and theasinensins, and flavones, encompassing kaempferol, quercetin, myricetin, and their respective glycosides. The inhibitory activities of fifty-eight tea polyphenols against 3CLpro were assessed in vitro, and eighteen phenolic compounds exhibited inhibitory effects on 3CLpro, with IC₅₀ values ranging from 9.8 μM to 61.1 μM. Among them, two types of tea polyphenols, catechin and flavoalkaloid derivatives, demonstrated superior inhibitory effects compared to other categories. The structure-activity relationship was further explored, and molecular docking analysis revealed that the differing inhibitory effects of catechin and flavoalkaloid derivatives were attributed to the variations in the number and positions of the hydrogen bond interactions with 3CLpro. This study provides a valuable understanding of tea polyphenols and supplies potential lead compounds for antiviral drugs. Full article

Now under Clusiaceae and Hypericaceae, Clusia and Hypericum were previously categorized under one family until they were divided in 2003 by the APG III system. The Clusia genus is characterized by the presence of tocotrienol derivatives with antiangiogenic properties, and only Hypericum perforatum tocochromanol content has been studied in the Hypericum genus. Twelve species were analyzed: H. aegypticum, H. calycinum, H. empetrifolium, H. lancasteri, H. olympicum f. minus ‘Sulphureum’, H. perforatum, H. xylosteifolium, C. fluminensis, C. minor, C. odorata, C. palmicida, and C. tocuchensis. Plant leaves were analyzed for their tocochromanol (α-, β-, γ-, and δ-tocotrienol and tocopherol) contents using a reverse-phase high-performance liquid chromatography with fluorescent light detector (RP-HPLC-FLD) method. While α-tocopherol (α-T) was present in the highest proportion, the leaves had significant tocotrienol (T3) contents. Following α-T, δ-T3 was present in most Clusia samples, and γ-T3 in most Hypericum samples, except H. olympicum, in which α-T3 followed. C. minor had the highest α-T (112.72 mg 100 g⁻¹) and total tocochromanol (141.43 mg 100 g⁻¹) content, followed by C. palmicida (65.97 and 82.96 mg 100 g⁻¹, respectively) and H. olympicum (α-T 32.08, α-T3 30.68, and total tocochromanols 89.06 mg 100 g⁻¹). The Hypericum genus is a valuable source of tocotrienols, with potential use after purification. Full article

The bunching onion is an important leafy vegetable, prized for its distinctive flavor and color. It is consumed year-round in Japan, where a stable supply is essential. However, in recent years, the challenges posed by climate change and global warming have resulted in adverse effects on bunching onions, including stunted growth, discoloration, and the development of leaf tipburn, threatening both crop quality and yield. Furthermore, as bunching onion belongs to the Allium genus, which includes globally significant vegetables such as onion and garlic, studying the impact of climate change on bunching onion serves as an ideal model. The insights gained can also be applied to other crops and regions. This study investigates the effects of different summer growth conditions on the metabolite profile of heat-tolerant bunching onions with dark green leaf blade coloration and examines their association with leaf tipburn. Pigment compound quantification, functional component analysis, leaf tipburn rate assessment, and widely targeted metabolome profiling were performed across two commercial ${\mathrm{F}}_1$ varieties, one purebred variety, and six Yamaguchi Prefecture-bred ${\mathrm{F}}_1$ lines under different growing conditions. The results obtained were subjected to comparative analyses based on the varieties and groups classified by high and low leaf tipburn rates. The results revealed that $\beta$-carotene accumulation peaked with May sowing and July harvest, while the highest accumulation of other pigment compounds was observed with May sowing and September harvest. Additionally, metabolome analysis related to leaf tipburn rates identified several organosulfur compounds, with gamma-glutamyl-propenyl cysteine sulfoxide emerging as one of the key compounds. Based on the intensity data, the fold change of this metabolite was calculated to be 1.66, indicating an increase in the leaf tipburn group compared to the control group. In the control groups, organosulfur compounds appeared to undergo turnover in preparation for stress response. In contrast, in the leaf tipburn groups, it is hypothesized that organosulfur compounds were converted into precursors of pungency, resulting in inadequate responses to stress. This study aims to elucidate the mechanisms through which organosulfur compounds transition into pungent compounds and to develop varieties with improved resistance to leaf tipburn. Full article

Food security is essential to ensure everyone can access sufficient nutritious food. Cereals and legumes are fundamental foods worldwide. Phaseolus vulgaris L., the common bean, is an essential staple food in many nations worldwide. However, it is vulnerable to fusariosis, a disease caused by the fungus Fusarium spp. that can significantly decrease crop quality and yield. To combat plant diseases, industrial residues and plant residues are valuable due to their bioactive compounds with biotechnological applications. This study proposes using ethanolic extracts with phytochemical compounds, such as flavonoids, different from those reported in essential oils, to reduce the growth of Fusarium species both in vitro and in vivo. Industrial residues that are produced after extracting essential oils offer a promising alternative to develop organic biopesticides, promoting more sustainable and environmentally friendly agriculture. Full article

The antimicrobial activity of an aqueous extract of the leaves of Schinus polygamus (cav.) Cabrera against microorganisms of food importance was evaluated. First, the leaf aqueous extract of Schinus polygamus was characterized, quantifying hydroxycinnamic acids and phenolic compounds. Then, a battery of strains was tested, including Escherichia coli ATCC 25922, Salmonella Typhimurium ATCC 14028, and Listeria monocytogenes ATCC 13932. Also, we tested wine spoilage yeasts such as Brettanomyces bruxellensis LAMAP2480, B. bruxellensis LAMAP1359, B. bruxellensis CECT1451, and Pichia guilliermondii NPCC1051. Tests were conducted using the kinetic curve of growth and cell viability counts. The results indicate that with 10% v/v of concentrated extract, it is possible to observe growth inhibition of all microorganisms studied, with statistically significant differences during the whole measurement time (70 h for bacteria and 145 h for yeast). Full article

Ajowan (Trachyspermum ammi L.) is considered a valuable spice and medicinal herb. In this study, the essential oil content and composition of the aerial parts of ajowan were investigated under different drying treatments (sun, shade, oven at 45 °C, oven at 65 °C, microwave, and freeze drying). Moreover, the phenolic content, flavonoid content, and antioxidant capacity of samples were also assessed. Fresh samples produced the highest essential oil content (1.05%), followed by those treated under sun (0.7%) and shade drying (0.95%). Based on gas chromatography–mass spectrometry (GC–MS), thirty compounds were determined in which thymol (34.84–83.1%), carvacrol (0.15–32.36%), p-cymene (0.09–13.66%), and γ-terpinene (3.12–22.58%) were the most abundant. Among the drying methods, freeze drying revealed the highest thymol content, followed by drying in a 45 °C oven. The highest TPC (total phenolic content) and TFC (total flavonoid content) were obtained in the fresh sample (38.23 mg TAE g⁻¹ dry weight (DW)) and in the sample oven-dried at 45 °C (7.3 mg QE g⁻¹ DW), respectively. Based on the HPLC results, caffeic acid (18.04–21.32 mg/100 gDW) and ferulic acid (13.102–19.436 mg/100 g DW) were the most abundant phenolic acids, while among flavonoids, rutin constituted the highest amount (10.26–19.88 mg/100 gDW). Overall, freeze drying was the most promising method of drying for preserving the phenolic (TPC) and flavonoid (TFC) compounds and oil components. Full article

Our research focuses on exploring the chemical composition and some biological properties of the essential oil derived from Syzygiella rubricaulis (Nees) Stephani, a bryophyte species. To conduct a comprehensive analysis, we utilized a DB5MS capillary column along with gas chromatography coupled to mass spectrometry (GC-MS) and flame ionization (GC-FID). The qualitative and quantitative examination revealed the presence of 50 compounds, with hydrocarbon sesquiterpenes (48.35%) and oxygenated sesquiterpenes (46.89%) being the predominant constituents. Noteworthy compounds identified include bicyclogermacrene (12.004%), cedranone <5-> (9.034%), spathulenol (6.835%), viridiflorol (6.334%), silphiperfol-5,7(14)-diene (6.216%), biotol <β-> (6.075%), guaiol (4.607%), viridiflorene (4.65%), and α-guaienol (3.883%). Furthermore, we assessed the antimicrobial, antioxidant, and anticholinesterase activity of the essential oil, revealing a compelling inhibitory effect against acetylcholinesterase (AChE) with an IC₅₀ value of 26.75 ± 1.03 µg/mL and a moderate antimicrobial (MIC 500 µg/mL, Enterococcus faecium, Lysteria monocytogenes) and antioxidant effect (ABTS: SC₅₀ 343.38 and DPPH 2650.23 µg/mL). These findings suggest the potential therapeutic application of the bryophyte essential oil in the treatment of Alzheimer’s disease due to its potent anticholinesterase properties. Full article

COVID-19, caused by SARS-CoV-2, has emerged as the most destructive emerging infectious disease of the 21st century. Vaccination is an effective method to combat viral diseases. However, due to the constant mutation of the virus, new variants may weaken the efficacy of vaccines. In the current field of new coronavirus research, viral protease inhibitors have emerged as a highly regarded therapeutic strategy. Nevertheless, existing viral protease inhibitors do not fully meet the therapeutic needs. Therefore, this paper turned to traditional Chinese medicine to explore new active compounds. This study focused on 24 isolated compounds from Acorus calamus L. and identified 8 active components that exhibited significant inhibitory effects on SARS-CoV-2 PLpro. Among these, the compound 1R,5R,7S-guaiane-4R,10R-diol-6-one demonstrated the best inhibitory activity with IC₅₀ values of 0.386 ± 0.118 μM. Additionally, menecubebane B and neo-acorane A exhibited inhibitory activity against both Mpro and PLpro proteases, indicating their potential as dual-target inhibitors. The molecular docking results confirmed the stable conformations of these compounds with the key targets and their good activity. ADMET and Lipinski’s rule analyses revealed that all the small molecule ligands possessed excellent oral absorption properties. This study provides an experimental foundation for the discovery of promising antiviral lead compounds. Full article

The genus Lepechinia (Lamiaceae) involves several aromatic shrubs that are distributed only in the American continent, inhabiting mountain areas, mainly in the Andean region of South America. Based on the PRISMA approach, we selected and critically analyzed 48 research articles. From a phytochemical point of view, most of the secondary metabolites reported in Lepechinia spp. are terpenes and terpenoids, with a few exceptions comprising flavonoids and other shikimic acid derivatives. On the one hand, sesquiterpenoids of the guajane, aromadendrane, eudesmane, and cadinane groups are characteristic of essential oils, together with (E)-β-caryophyllene as the main representative of its chemical family. On the other hand, abietane diterpenoids are the prevalent compounds described in non-volatile fractions. Many biological activities and traditional medical uses have been reported for both pure metabolites and complex mixtures (e.g., essential oils). Regarding ethno-medical uses, the treatment of muscle pain, headache, toothache, diabetes mellitus, uterine tumors, uterine infections, and diarrhea has been reported. Concerning their verified biological activities, insecticidal, antifungal, antioxidant, and anticholinesterase properties have been described. Furthermore, some data concerning anti-herpetic activity have been reported. Full article

The results of the most recent investigation of triterpenoid-based antiviral agents namely in the HIV-1 and HSV-1 treatment were reviewed and summarized. Several key historical achievements are included to stress consequences and continuity in this research. Most of the agents studied belong to a series of compounds derived from betulin or betulinic acid, and their synthetic derivative is called bevirimat. A termination of clinical trials of bevirimat in Phase IIb initiated a search for more successful compounds partly derived from bevirimat or designed independently of bevirimat structure. Surprisingly, a majority of bevirimat mimics are derivatives of betulinic acid, while other plant triterpenoids, such as ursolic acid, oleanolic acid, glycyrrhetinic acid, or other miscellaneous triterpenoids, are relatively rarely involved in a search for a novel antiviral agent. Therefore, this review article is divided into three parts based on the leading triterpenoid core structure. Full article

Diterpenes from the Euphorbia genus are known for their ability to regulate the protein kinase C (PKC) family, which mediates their ability to promote the proliferation of neural precursor cells (NPCs) or neuroblast differentiation into neurons. In this work, we describe the isolation from E. resinifera Berg latex of fifteen 12-deoxyphorbol esters (1–15). A triester of 12-deoxy-16-hydroxyphorbol (4) and a 12-deoxyphorbol 13,20-diester (13) are described here for the first time. Additionally, detailed structural elucidation is provided for compounds 3, 5, 6, 14 and 15. The absolute configuration for compounds 3, 4, 6, 13, 14 and 15 was established by the comparison of their theoretical and experimental electronic circular dichroism (ECD) spectra. Access to the above-described collection of 12-deoxyphorbol derivatives, with several substitution patterns and attached acyl moieties, allowed for the study of their fragmentation patterns in the collision-induced dissociation of multiple ions, without precursor ion isolation mass spectra experiments (HRMS^E), which, in turn, revealed a correlation between specific substitution patterns and the fragmentation pathways in their HRMS^E spectra. In turn, this allowed for a targeted UHPLC-HRMS^E analysis and a biased non-targeted UHPLC-HRMS^E analysis of 12-deoxyphorbols in E. resinifera latex which yielded the detection and identification of four additional 12-deoxyphorbols not previously isolated in the initial column fractionation work. One of them, identified as 12-deoxy-16-hydroxyphorbol 20-acetate 13-phenylacetate 16-propionate (20), has not been described before. Full article

A comprehensive comparative analysis of the carbohydrate composition (soluble sugars and pectins) of fruit tissues of Malus baccata, Malus mandshurica, Malus chamardabanica, and Malus sachalinensis, characteristic of the vast territory of Eastern Siberia and the Far East, was carried out. It was shown that a large part of the soluble carbohydrates of the studied species were represented by transport sugars—sorbitol and sucrose. These compounds also provided the main variability in the carbohydrate composition of fruits in the studied material. The polymers pectins and protopectins isolated from the studied fruits were highly methoxylated (up to 60–70%), and their content averaged about 6% of dry weight. The greatest length of pectin polymers was found in the fruit tissues of M. chamardabanica and M. sachalinensis. Data on elemental analysis of fractions of pectins and protopectins of all studied species showed the absence of potentially toxic concentrations of heavy metals. Of note is the rather high content of calcium in both polymer fractions of the four studied species, while its content in protopectin is significantly higher. In addition, in all cases, the presence of low-molecular-weight oligosaccharide molecules with a low-dispersed linear structure was revealed in the tissues of the fruits. It is worth noting that the high content of ascorbic acid was observed in the fruits of all studied species. In addition to being of fundamental interest, information about the carbohydrate composition of the wild Malus species can be useful for apple breeding when choosing sources of genes underlying useful traits. Full article

Tropane alkaloids (TAs) are large secondary metabolite alkaloids that find extensive applications in the synthesis of antidotes, anesthetics, antiemetics, motion sickness drugs, and antispasmodics. The current production method primarily depends on extraction from medicinal plants of the Solanaceae family. Elicitation, as a highly effective biotechnological approach, offers significant advantages in augmenting the synthesis of secondary metabolites. The advantages include its simplicity of operation, low cost, and reduced risk of contamination. This review focuses on the impact of elicitation on the biosynthesis of TAs from three aspects: single-elicitor treatment, multiple-elicitor treatment, and the combination of elicitation strategy with other strategies. Some potential reasons are also proposed. Plant hormones and growth regulators, such as jasmonic acid (JA), salicylic acid (SA), and their derivatives, have been extensively employed in the separate elicitation processes. In recent years, novel elicitors represented by magnetic nanoparticles have emerged as significant factors in the investigation of yield enhancement in TAs. This approach shows promising potential for further development. The current utilization of multi-elicitor treatment is constrained, primarily relying on the combination of only two elicitors for induction. Some of these combinations have been found to exhibit synergistic amplification effects. However, the underlying molecular mechanism responsible for this phenomenon remains largely unknown. The literature concerning the integration of elicitation strategy with other strategies is limited, and several research gaps require further investigation. In conclusion, the impact of various elicitors on the accumulation of TAs is well-documented. However, further research is necessary to effectively implement elicitation strategies in commercial production. This includes the development of stable bioreactors, the elucidation of regulatory mechanisms, and the identification of more potent elicitors. Full article