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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (28 February 2026) | Viewed by 60657

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Editors

Dr. Hazem Salaheldin Elshafie

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Guest Editor

Department of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy
Interests: natural products; microbiology; plant pathology; antimicrobial activities; bioactive secondary metabolites
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Dr. Lucia Caputo

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Co-Guest Editor

Department of Pharmacy, University of Salerno, Fisciano, Italy
Interests: plant extracts; essential oil; biological activity; weed management; natural compound identification
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue will provide up-to-date information on natural products and their possible applicative fields related to their biological activities. In recent years, there has been an increasing amount of interest in natural products, which are important sources of novel drug research and development. Contributions to this Special Issue may cover all advances related to natural product discovery, including the possible use of essential oils and extracts in new fields.

This Special Issue, “Natural Products: Isolation, Analysis and Biological Activity,” aims to publish original scientific articles on obtaining, identifying, and applying natural products in healthcare, agriculture, and foods.

Dr. Hazem Salaheldin Elshafie
Dr. Lucia Caputo
Guest Editors

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

essential oils
plant extracts
biological activities
antiproliferative activity
enzymatic inhibitor activity
phytotoxic activity
bioactive compounds in natural products
secondary metabolites
structure–activity relationships
antimicrobial activity
phytopathogens

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Related Special Issues

Natural Products: Isolation, Analysis and Biological Activity in Molecules (8 articles)
Natural Products: Isolation, Analysis and Biological Activity, 3rd Edition in Molecules (2 articles)

Published Papers (8 papers)

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Research

Jump to: Review

22 pages, 1735 KB

Open AccessArticle

Biocontrol of Fusarium and Other Fungal Diseases of Cereals Using Bacterial Compounds and Plant Extracts

by Joanna Horoszkiewicz, Ewa Jajor, Marek Korbas, Jakub Danielewicz, Jan Bocianowski, Marzena Mikos-Szymańska, Tomasz Szymczak, Jagoda Kucharska, Monika Kobiałka and Marcin Podleśny

Molecules 2026, 31(10), 1761; https://doi.org/10.3390/molecules31101761 - 20 May 2026

Viewed by 589

Abstract

Plant extracts and microbiological supernatants were subjected to qualitative and compositional analyses to characterize their bioactive profiles and assess their potential agricultural applications. The garlic (Allium sativum) extract was rich in allicin and selected free amino acids, contained betulin as the dominant triterpene, and displayed a favorable elemental profile with high levels of potassium, phosphorus, sulfur, calcium, and magnesium, with no detectable heavy metals. Detectable amounts of B-group vitamins and vitamin E isoforms were also identified. Qualitative phytochemical screening confirmed the presence of saponins and flavonoids in the garlic extract. The Jerusalem artichoke (Helianthus tuberosus) extract exhibited a significantly higher total phenolic content compared to the garlic extract, with qualitative analysis confirming the presence of saponins, tannins, and flavonoids, suggesting a broader spectrum of bioactive compounds. The two bacterial supernatants were characterized by HPLC analysis and differed in their metabolic profiles: the Enterobacter sp. fermentation broth contained glycerol, 2,3-butanediol, and acetic acid, while the Paenibacillus sp. supernatant additionally contained lactic acid, ethanol, and succinic acid, reflecting distinct fermentation pathways. The in vitro and greenhouse studies aimed to evaluate biological preparations for controlling wheat diseases caused by fungi of the Fusarium genus as well as diseases affecting the stem base. Plant extracts (garlic—Allium sativum, Jerusalem artichoke—Helianthus tuberosus) and supernatants (fermentation broths) obtained with the Paenibacillus and Enterobacter bacteria were tested at three concentrations. In laboratory experiments, the degree of inhibition of the growth of the mycelium of the tested fungal species was determined, while in greenhouse studies, the effectiveness in limiting the development of stem base diseases and the impact of the applied biopreparations on plant growth were evaluated. Among the plant extracts, H. tuberosus demonstrated superior antifungal activity, achieving up to 100% inhibition of R. cerealis mycelial growth at 10% concentration and reducing disease severity by 34.3% compared to the untreated control under greenhouse conditions. Paenibacillus sp. supernatant demonstrated strong in vitro antifungal activity. The results indicate that H. tuberosus extract represents a promising candidate for further field evaluation as a component of sustainable wheat protection programs. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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15 pages, 1935 KB

Open AccessArticle

L-Tryptophan Stimulates Bioactive Metabolite Accumulation and Cell Wall Remodelling in Flax Callus Cultures

by Kornelia L. Tudruj, Michał Piegza, Lucyna Dymińska, Maja Słupczyńska and Magdalena Wróbel-Kwiatkowska

Molecules 2026, 31(8), 1229; https://doi.org/10.3390/molecules31081229 - 8 Apr 2026

Viewed by 700

Abstract

While L-tryptophan is a precursor of plant growth regulators, its effects on secondary metabolism, amino acid profile and cell wall organization in flax callus remain underexplored. This study aimed to optimize flax callus shaken cultures and evaluate the impact of L-tryptophan (0.1 mM and 1 mM) on structural properties of plant cell walls in tested callus using Fourier transform infrared spectroscopy. The impact of L-tryptophan on callus proliferation and metabolism was also determined, because amino acids (among them L-tryptophan) can promote the growth of callus. The results showed that 1 mM L-tryptophan is an effective elicitor, which stimulates flax callus to accumulate larger amounts of bioactive compounds, especially carotenoids and polyphenols, than control callus cultured without L-tryptophan. A lower concentration of L-tryptophan (0.1 mM) slightly improved the level of determined secondary metabolites (except flavonoids). The effect of L-tryptophan on polymers in plant cell walls was investigated. The data confirm that the plant cell wall is a dynamic structure, capable of remodelling in response to growth conditions and external agents. L-tryptophan (0.1 and 1 mM) reduced cellulose levels and induced structural changes in cellulose compared to the untreated control. The structural analyses also suggested a decrease in lignin level and increase in pectin amounts in flax callus after tryptophan addition in comparison to control callus. The results may reflect the relationship between tryptophan and auxins (which are derived from tryptophan) and confirm the role of these metabolites in shaping the structure of the plant cell wall. In fact, an increase in tryptophan level was confirmed in flax callus in tested experimental conditions (supplementation of cultures with both doses of L-tryptophan). These findings have practical significance, because L-tryptophan is also used as a fertilizer or component of fertilizers in plant cultivation. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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19 pages, 9255 KB

Open AccessArticle

Impact of Scutellonema curcumae sp. n. (Nematoda: Hoplolaimidae) on the Phytochemical Profile and Biological Activities of Turmeric (Curcuma longa L.)

by Tu Thi Dinh, Quan Minh Pham, Long Quoc Pham, Chi Kim Ngo, Van Thi Thuy Nguyen, Thuong Thi Le Hoang, Tu Ngoc Ly, Linh Ngoc Nguyen, Thao Thi Phuong Nguyen and Lam Tien Do

Molecules 2026, 31(6), 920; https://doi.org/10.3390/molecules31060920 - 10 Mar 2026

Viewed by 589

Abstract

A new spiral nematode species, Scutellonema curcumae sp. n., was identified from the rhizosphere of turmeric (Curcuma longa L.) in the Western Highlands of Vietnam. Integrative taxonomical analysis, combining detailed morphology and molecular characterization (ITS, 28S D2–D3 rDNA, and COI mtDNA), confirmed its distinctiveness. Scutellonema curcumae sp. n. is characterized by a unique combination of a spiral body, a hemispherical lip region with four annuli, a robust stylet, and a rounded tail with a prominent scutellum, forming a highly divergent lineage within the genus. Beyond its description, this study reveals a significant inverse correlation between nematode population density and the phytochemical quality of the host. High infestation levels were associated with a marked decline in total curcuminoid content. Notably, lower nematode density favored a specific shift in the curcuminoid profile, with bisdemethoxycurcumin levels increasing by up to 250%. These phytochemical alterations directly influenced the therapeutic potential of the rhizomes: lower infestation levels resulted in significantly enhanced antioxidant capacity (lower SC₅₀ values) and cytotoxic activity (lower IC₅₀ against HepG2 and A549 cell lines). This work represents the first report of a Scutellonema species associated with turmeric in Vietnam and underscores its detrimental impact on the medicinal and nutraceutical value of the crop. Our findings suggest that effective nematode management is crucial not only for yield protection but as a strategic intervention in precision agriculture to optimize the secondary metabolite profiles of medicinal plants. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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32 pages, 2455 KB

Open AccessArticle

Bifunctional Systems of Amelanchier alnifolia Leaves Extract-Oligosaccharides with Prebiotic and Antidiabetic Benefits

by Anna Gościniak, Anna Sip, Piotr Szulc and Judyta Cielecka-Piontek

Molecules 2025, 30(16), 3327; https://doi.org/10.3390/molecules30163327 - 8 Aug 2025

Cited by 3 | Viewed by 1551

Abstract

Amelanchier alnifolia is a plant known for its nutritional and bioactive properties. Its leaves contain a high concentration of active compounds with significant antioxidant and antidiabetic effects, including strong α-glucosidase inhibitory potential. The combination of these bioactive leaf extracts with prebiotic substances, such as fructooligosaccharides (FOS), galactooligosaccharides (GOS), and chitooligosaccharides (COS), enables the development of functional systems with enhanced beneficial properties. In this study, process optimization for leaves extraction was performed using a Plackett–Burman screening design, which identified key parameters for further optimization using the Box–Behnken design. The optimal extraction conditions were determined as follows: methanol content 58.06%, solid-to-solvent ratio 26.03 m/v, and extraction time 73.56 min. These conditions yielded the highest the total phenolic content (TPC). A comparative analysis of different cultivars revealed significant variations in polyphenol content among them. The formulated lyophilized systems with GOS, FOS and COS positively influenced the chlorogenic acid release profile, while maintaining the extract’s antidiabetic and antioxidant properties. FT-IR analysis confirmed the molecular interactions responsible for these effects. The prebiotic effectiveness of the systems was quantitatively evaluated using two key parameters: the prebiotic index (PI), and the prebiotic activity score (PAS). Microbiological analyses demonstrated the beneficial effects of prebiotic-enriched systems characterized by better prebiotic action on Bifidobacterium strains than the pure extract. These findings suggest that A. alnifolia leaf extracts, in combination with prebiotics, could serve as promising functional ingredients with potential applications in health-promoting and antidiabetic formulations. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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16 pages, 2147 KB

Open AccessArticle

Stress-Relieving Effects of Green Tea Depend on the Ratio of Its Special Ingredients and the Infusion Conditions

by Keiko Unno, Kyoko Taguchi, Tomoko Matsuda and Yoriyuki Nakamura

Molecules 2024, 29(19), 4553; https://doi.org/10.3390/molecules29194553 - 25 Sep 2024

Cited by 3 | Viewed by 6872

Abstract

Theanine, an amino acid unique to tea leaves, has been reported to exhibit stress-relieving effects. However, the stress-relieving effects of theanine (T) are greatly inhibited by caffeine (C) and epigallocatechin gallate (E), the main components of green tea, while being enhanced by arginine (A). Animal and clinical studies using matcha tea have shown that it can alleviate stress if the molar ratio of C and E against T and A (CE/TA) is less than 2. In general, the CE/TA ratio in tea leaves is reflected by the CE/TA ratio in the infused solution; however, it is not clear what infusion conditions would be expected to ensure a stress-relieving effect. In this study, to examine the stress-relieving effect of green-tea-infused solutions, the CE/TA ratio was measured under different infusion conditions. Furthermore, a study using a model solution consisting of C, E, T, and A revealed that a CE/TA ratio of at least less than 2 and a T content greater than 0.23 mM were required for stress reduction. Based on these results, we identified tea leaves and their infusion conditions that can be expected to reduce stress. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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17 pages, 3490 KB

Open AccessArticle

Lupeol-3-carbamate Derivatives: Synthesis and Biological Evaluation as Potential Antitumor Agents

by Shuang Tian, Yinxu Zhao, Siqi Deng, Liman Hou, Juan Song, Ming Wang and Ming Bu

Molecules 2024, 29(17), 3990; https://doi.org/10.3390/molecules29173990 - 23 Aug 2024

Cited by 13 | Viewed by 2878

Abstract

In the following study, a series of new lupeol-3-carbamate derivatives were synthesized, and the structures of all the newly derived compounds were characterized. The new compounds were screened to determine their anti-proliferative activity against human lung cancer cell line A549, human liver cancer cell line HepG2, and human breast cancer cell line MCF-7. Most of the compounds were found to show better anti-proliferative activity in vitro than lupeol. Among them, obvious anti-proliferation activity (IC₅₀ = 5.39~9.43 μM) was exhibited by compound 3i against all three tumor cell lines. In addition, a salt reaction was performed on compound 3k (IC₅₀ = 13.98 μM) and it was observed that the anti-proliferative activity and water solubility of compound 3k·CH₃I (IC₅₀ = 3.13 μM), were significantly enhanced subsequent to the salt formation process. The preliminary mechanistic studies demonstrated that apoptosis in HepG2 cells was induced by compound 3k·CH₃I through the inhibition of the PI3K/AKT/mTOR pathway. In conclusion, a series of new lupeol-3-carbamate derivatives were synthesized via the structural modification of the C-3 site of lupeol, thus laying a theoretical foundation for the design of this new anticancer drug. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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Review

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33 pages, 2757 KB

Open AccessReview

Bridging Two Worlds: Structural and Pharmacological Aspects of Natural Triterpenoid Dimers: Pristimerin-Pristimerin-Type Dimers

by Andrzej Günther and Barbara Bednarczyk-Cwynar

Molecules 2026, 31(9), 1386; https://doi.org/10.3390/molecules31091386 - 23 Apr 2026

Viewed by 847

Abstract

This review summarizes current knowledge on naturally occurring pristimerin-pristimerin triterpenoid dimers, a rare and structurally diverse class of secondary metabolites reported mainly from Celastraceae species. Known dimers are compiled with emphasis on botanical sources and key architectural features, including the variety of interunit linkages, regio- and stereochemical diversity, and distinct isomeric forms (including atropisomerism). Major advances in structure elucidation and structural revisions are discussed, highlighting the role of modern spectroscopic tools—particularly 2D NMR methods and chiroptical techniques—in resolving connectivity and absolute configuration, and in correcting several earlier assignments. Proposed biosynthetic scenarios are outlined, focusing on the reactivity of the quinone-methide motif and its interconversion with 2,3-diketone forms, as well as (hetero) Diels-Alder-type processes; selected biomimetic studies are summarized as supportive evidence for these pathways. A critical overview of available biological data indicates that many pristimerin dimers display limited activity in common antimicrobial and cytotoxicity assays when compared with monomeric congeners, which may point to alternative ecological roles or storage/transport functions in planta. Finally, key knowledge gaps and future directions are identified, including improved isolation coverage, rigorous synthetic/biomimetic work, and broader pharmacological screening beyond standard panels. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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34 pages, 2238 KB

Open AccessReview

Epigallocatechin Gallate (EGCG): Pharmacological Properties, Biological Activities and Therapeutic Potential

by Lucia Capasso, Luigi De Masi, Carmina Sirignano, Viviana Maresca, Adriana Basile, Angela Nebbioso, Daniela Rigano and Paola Bontempo

Molecules 2025, 30(3), 654; https://doi.org/10.3390/molecules30030654 - 1 Feb 2025

Cited by 179 | Viewed by 45154

Abstract

Epigallocatechin gallate (EGCG), the predominant catechin in green tea, comprises approximately 50% of its total polyphenol content and has garnered widespread recognition for its significant therapeutic potential. As the principal bioactive component of Camellia sinensis, EGCG is celebrated for its potent antioxidant, anti-inflammatory, cardioprotective, and antitumor properties. The bioavailability and metabolism of EGCG within the gut microbiota underscore its systemic effects, as it is absorbed in the intestine, metabolized into bioactive compounds, and transported to target organs. This compound has been shown to influence key physiological pathways, particularly those related to lipid metabolism and inflammation, offering protective effects against a variety of diseases. EGCG’s ability to modulate cell signaling pathways associated with oxidative stress, apoptosis, and immune regulation highlights its multifaceted role in health promotion. Emerging evidence underscores EGCG’s therapeutic potential in preventing and managing a range of chronic conditions, including cancer, cardiovascular diseases, neurodegenerative disorders, and metabolic syndromes. Given the growing prevalence of lifestyle-related diseases and the increasing interest in natural compounds, EGCG presents a promising avenue for novel therapeutic strategies. This review aims to summarize current knowledge on EGCG, emphasizing its critical role as a versatile natural bioactive agent with diverse clinical applications. Further exploration in both experimental and clinical settings is essential to fully unlock its therapeutic potential. Full article

(This article belongs to the Special Issue Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition)

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