Phenolic compounds and ecdysteroids of Diplazium esculentum (Retz.) Sw. (Athyriaceae) from Japan and their chemotaxonomic significance

Insights into Chemical Diversity and Potential Health-Promoting Effects of Ferns

The scientific community is focusing on how to enhance human health and immunity through functional foods, and dietary supplements are proven to have a positive as well as a protective effect against infectious and chronic diseases. Ferns act as a taxonomical linkage between higher and lower plants and are endowed with a wide chemical diversity not subjected to sufficient scrutinization before. Even though a wealth of traditional medicinal fern uses were recorded in Chinese medicine, robust phytochemical and biological investigations of these plants are lacking. Herein, an extensive search was conducted using the keywords ferns and compounds, ferns and NMR, ferns and toxicity, and the terms ferns and chemistry, lignans, Polypodiaceae, NMR, isolation, bioactive compounds, terpenes, phenolics, phloroglucinols, monoterpenes, alkaloids, phenolics, and fatty acids were utilized with the Boolean operators AND, OR, and NOT. Databases such as PubMed, Web of Science, Science Direct, Scopus, Google Scholar, and Reaxys were utilized to reveal a wealth of information regarding fern chemistry and their health-promoting effects. Terpenes followed by phenolics represented the largest number of isolated active compounds. Regarding the neuroprotective effects, Psilotium, Polypodium, and Dryopteris species possessed as their major phenolics component unique chemical moieties including catechins, procyanidins, and bioflavonoids. In this updated chemical review, the pharmacological and chemical aspects of ferns are compiled manifesting their chemical diversity in the last seven years (2017-2024) together with a special focus on their nutritive and potential health-promoting effects.

Box-Behnken Design-Based Optimization of Phytochemical Extraction from Diplazium esculentum (Retz.) Sw. Associated with Its Antioxidant and Anti-Alzheimer's Properties

A previous study reported that the ethanolic extract of the edible fern, Diplazium esculentum (Retz.) Sw. (DE), obtained from a non-optimized extraction condition exhibited anti-Alzheimer's disease (AD) properties through the inhibition of a rate-limiting enzyme in amyloid peptide formation, β-secretase-1 (BACE-1). Nevertheless, a non-optimized or suboptimal extraction may lead to several issues, such as a reduction in extraction efficiency and increased time and plant materials. In this study, extraction of the DE was optimized to obtain appropriate BACE-1 inhibition using a Box-Behnken design (BBD) and response surface methodology (RSM). Data revealed that the optimal extraction condition was 70% (v/v) aqueous ethanol, 50 min extraction time, 30 °C extraction temperature, and 1:30 g/mL solid/liquid ratio, giving BACE-1 inhibition at 56.33%. In addition, the extract also exhibited significant antioxidant activities compared to the non-optimized extraction. Metabolomic phytochemical profiles and targeted phytochemical analyses showed that kaempferol, quercetin, and their derivatives as well as rosmarinic acid were abundant in the extract. The optimized DE extract also acted synergistically with donepezil, an AD drug suppressing BACE-1 activities. Data received from Drosophila-expressing human amyloid precursor proteins (APPs) and BACE-1, representing the amyloid hypothesis, showed that the optimized DE extract penetrated the fly brains, suppressed BACE-1 activities, and improved locomotor functions. The extract quenched the expression of glutathione S transferase D1 (GSTD1), inositol-requiring enzyme (IRE-1), and molecular chaperone-binding immunoglobulin (Bip), while donepezil suppressed these genes and other genes involved in antioxidant and endoplasmic reticulum (ER) stress response, including superoxide dismutase type 1 (SOD1), activating transcription factor 6 (ATF-6), and protein kinase R-like endoplasmic reticulum kinase (PERK). To sum up, the optimized extraction condition reduced extraction time while resulting in higher phytochemicals, antioxidants, and BACE-1 inhibitors.

The traditional utilization, biological activity and chemical composition of edible fern species

ETHNOPHARMACOLOGICAL RELEVANCE

Ferns form an important part of the human diet. Young fern fiddleheads are mostly consumed as vegetables, while the rhizomes are often extracted for starch. These edible ferns are also often employed in traditional medicine, where all parts of the plant are used, mostly to prepare extracts. These extracts are applied either externally as lotions and baths or internally as potions, decoctions and teas. Ailments traditionally treated with ferns include coughs, colds, fevers, pain, burns and wounds, asthma, rheumatism, diarrhoea, or skin diseases (eczema, rashes, itching, leprosy).

AIM OF THE REVIEW

This review aims to compile the worldwide knowledge on the traditional medicinal uses of edible fern species correlating to reported biological activities and isolated bioactive compounds.

MATERIALS AND METHODS

The articles and books published on edible fern species were searched through the online databases Web of Science, Pubmed and Google Scholar, with critical evaluation of the hits. The time period up to the end of 2022 was included.

RESULTS

First, the edible fern species were identified based on the literature data. A total of 90 fern species were identified that are eaten around the world and are also used in traditional medicine. Ailments treated are often associated with inflammation or bacterial infection. However, only the most common and well-known fern species, were investigated for their biological activity. The most studied species are Blechnum orientale L., Cibotium barometz (L.) J. Sm., Diplazium esculentum (Retz.) Sw., Marsilea minuta L., Osmunda japonica Thunb., Polypodium vulgare L., and Stenochlaena palustris (Burm.) Bedd. Most of the fern extracts have been studied for their antioxidant, anti-inflammatory and antimicrobial activities. Not surprisingly, antioxidant capacity has been the most studied, with results reported for 28 edible fern species. Ferns have been found to be very rich sources of flavonoids, polyphenols, polyunsaturated fatty acids, carotenoids, terpenoids and steroids and most of these compounds are remarkable free radical scavengers responsible for the outstanding antioxidant capacity of fern extracts. As far as clinical trials are concerned, extracts from only three edible fern species have been evaluated.

CONCLUSIONS

The extracts of edible fern species exert antioxidant anti-inflammatory and related biological activities, which is consistent with their traditional medicinal use in the treatment of wounds, burns, colds, coughs, skin diseases and intestinal diseases. However, studies to prove pharmacological activities are scarce, and require chemical-biological standardization. Furthermore, correct botanical classification needs to be included in publications to simplify data acquisition. Finally, more in-depth phytochemical studies, allowing the linking of traditional use to pharmacological relevance are needed to be done in a standardized way.

Phytochemical profiling and biological activities of Diplazium esculentum (Retz.) Sw.: an edible vegetable fern

OBJECTIVES

Diplazium esculentum (Retz.) Sw. is an edible vegetable fern of the Himalayan region with high nutritional and therapeutic value owing to its richness in various secondary metabolites and both macro and micronutrients.

CONTENT

This updated review discusses the general traditional use, ethnopharmacology, phytochemistry, nutritional value, pharmacology, and toxicity concerns of D. esculentum.

SUMMARY

The plant parts, viz. rhizomes, shoots, fronds and leaves, have immense ethnomedicinal importance, being traditionally used to cure several health disorders. Among other pharmacological effects, this botanical reveals excellent anti-inflammatory, analgesic, antifungal, antibacterial, antioxidant, anti-leishmanial, antioxidant, anaphylactic, antipyretic, anthelmintic and hepatoprotective activities, directly attributed to the presence of many secondary metabolites. From a pharmacological point of view, the excellent antioxidant potential of D. esculentum suggests its promising use for nutraceutical or functional food formulation purposes.

OUTLOOK

Considering the evidences on popular ethnomedicinal uses of D. esculentum as an edible vegetable, its immense bio-potential, and multiple pharmacological roles, there is a huge need to evaluate its therapeutic applications in light of standard clinical trials.

Diplazium esculentum (Retz.) Sw.: Ethnomedicinal, Phytochemical, and Pharmacological Overview of the Himalayan Ferns

The genus Diplazium (family: Athyriaceae) comprises approximately 350 species of pteridophytes. Diplazium esculentum (Retz.) Sw. is an important member of this genus and commonly known as a wild vegetable in the Himalayan and sub-Himalayan communities. According to the literature analysis, D. esculentum was traditionally used for the prevention or treatment of several diseases such as diabetes, smallpox, asthma, diarrhea, rheumatism, dysentery, headache, fever, wounds, pain, measles, hypertension, constipation, oligospermia, bone fracture, and glandular swellings. Various extracts of D. esculentum were evaluated to elucidate their phytochemical and pharmacological activities. A wide array of pharmacological properties such as antioxidant, antimicrobial, antidiabetic, immunomodulatory, CNS stimulant, and antianaphylactic activities have been recognized in different parts of D. esculentum. The review covers a systematic examination of pharmacognosy, phytochemistry, and pharmacological applications of D. esculentum, but scientifically, it is not fully assessed regarding complete therapeutic effects, toxicity, and safety in the human body. The published literature on D. esculentum and its therapeutic properties were collected from different search engines including Wiley online, PubMed, Springer Link, Scopus, Science Direct, Web of Science, Google Scholar, and ACS publications by using specific terms such as "Diplazium esculentum, bioactive compounds, biological activities and health benefits" from 1984 to 2021 (March). Therefore, further studies are required to identify the detailed action mechanism of D. esculentum in vitro/in vivo, and also, more studies should focus on conservation, cultivation, and sustainable utilization of the species.