A new glucosidic phthalide from Helichrysum microphyllum subsp. tyrrhenicum from La Maddalena Island (Sardinia, Italy)

Helichrysum microphyllum subsp. tyrrhenicum: a possible correlation between small volatile compounds and phloroglucinol content

The chemical composition of the flowered aerial parts of four samples of Helichrysum microphyllum subsp. tyrrhenicum collected in South-West Sardinia was investigated with a combined focus on volatile constituents and phloroglucinols to find a possible correlation with the presence of arzanol endowed with the major anti-inflammatory activity. The volatile constituents were analysed by GC-MS as EO-HD and with HS-SPME identifying a total of 95 compounds of which 70 and 77 by EO-HD and HS-SPME respectively. The profile of the non-volatile phloroglucinols was investigated by HPLC-MS/MS. Arzanol concentrations ranged from 2.79 to 21.87 mg/g, helipyrone showed the same trend but in lower concentration. Surprisingly, leaves and stems contain higher concentration of phloroglucinols than the flowers. The concentration of arzanol was positively correlated to the one of γ-curcumene and ethylpyrone in the EO, while a negative correlation was observed with the monoterpene limonene and linalool as well as with the sesquiterpene 5-eudesmen-11-ol.

Phytochemical constituents, ferric reducing and radical scavenging activities of helichrysm caespititium

Helichrysm caespititium is used for the treatment of viral infections and respiratory ailments. This study aimed to determine the phytochemical constituents and antioxidants (using ABTS, DPPH and FRAP) of H. caespititium water and methanol extracts. The phytochemical analysis revealed the presence of flavonoids, phytosterols, tannins, glycosides etc. Whilst the alkaloids were absent. Quantitative analysis of total phenols using both methanol and water extracts yielded high values of (839,1 and 531) GA/mg indicating rich phytochemical constituents from this plant. Whilst flavonoids from methanol and water extracts yielded (324 and 58) mg GA/mg, respectively. Results obtained from FRAP water and methanol extracts were 20,42% and 2,36% respectively; DPPH water and methanol extracts results were 92,62% and 80,56% respectively; and ABTS water and methanol extracts were 93,64% and 97,68%, respectively. These findings support the potential of H. caespititium as the potential source for the development of antioxidant-based therapies and health-promoting products.

Volatile Organic Compounds (VOCs) Diversity in the Orchid Himantoglossum robertianum (Loisel.) P. Delforge from Sardinia (Italy)

Volatile Organic Compounds (VOCs) are produced by plants to address a variety of physiological and ecological tasks (among others, stress resistance, and pollinator attraction). Genetics is a key factor in determining plants’ VOCs content and emission, nevertheless, environment strongly influences VOCs profiles in plants. Orchids are a widespread group of plants that colonize diverse environments and rely on complex and refined pollination mechanisms to reproduce. Orchids VOCs are rarely studied and discussed in relation to growing conditions. In the present study, we compare the volatile profiles of inflorescences of Himantoglossum robertianum (Loisel.) P. Delforge sampled in six ecologically diverse populations on Sardinia Island (Italy). The essential oils obtained by steam distillation were characterized by GC-FID and GC-MS analysis. A total of 79 compounds were detected, belonging to the chemical classes of saturated hydrocarbons, esters, alcohols, ketones, unsaturated hydrocarbons, sesquiterpenes, oxygenated terpenes, terpenes, acids, and aldehydes. Multivariate statistics separated H. robertianum populations based on their chemical profiles. Differences were positively linked to the distance separating populations and reflected climatological features of the sampling sites. Interestingly, our results differed from those available in the literature, pointing out the high variability of VOCs profiles in this food-deceptive orchid.

Ethnopharmacobotany and Diversity of Mediterranean Endemic Plants in Marmilla Subregion, Sardinia, Italy

Human populations in various regions across the world exploit the medicinal properties of plants to treat a wide variety of diseases. Areas with both high rates of endemic taxa and persisting traditional uses of the local botanical resources are key sites for the investigation of Traditional Botanical Knowledge (TBK). Commonly, in these areas, information regarding the medicinal properties of native plants has been transmitted orally from generation to generation, however, a rapid decline in this knowledge has been observed, which can be attributed to socio-economic changes in recent years. The Mediterranean basin is one such site, where human history is intimately entwined with nature. The unique geographical situation and unrivaled environmental heterogeneity of the area, have allowed both the development of diverse civilizations as well as providing the basis for the evolution of extraordinary biodiversity. The Mediterranean basin can therefore be considered a global hotspot of endemic vascular plants, and of traditional knowledge of medicinal and aromatic species. This study researches the historical subregion of Marmilla (central-southern Sardinia, Italy), which was chosen because of its specific cultural and demographic characteristics: i.e., prolonged isolation and extreme longevity of the inhabitants of the area. Semi-structured interviews were conducted with 145 people from the region, and 137 medicinal plants belonging to 62 families were identified, of which around 57,3% were taxa exclusive to the Mediterranean Basin. Findings showed that the most used parts of the plant were the leaves (49%), while as far as preparations are concerned, decoction (50%) was the most used to prepare medicinal formulations, making this the highest number of medico-botanical taxa reported in a study carried out in Sardinia using a similar methodology. In addition, this study contributes towards preventing the loss of TBK by documenting the medicinal traditions, passed down orally for centuries, in the words of the participants, shedding new light on the traditional knowledge of the inhabitants of the island. The findings lay the foundations for future applied studies in the fields of phytotherapy and phytochemical investigation.

Recent advances in natural phthalides: Distribution, chemistry, and biological activities

Phthalides, an important class of bioactive natural products, are widely distributed in plants, fungi, lichens, and liverworts. Amon them, n-butylphthalide, a phthalide monomer, has been approved to cure ischemic stroke. Owing to their good bioactivities in anti-microbial, anti-inflammatory, anti-tumor, anti-diabetic, and other aspects, a large number of researches have been conducted on phthalides from nature materials. In recent years, hundreds of novel natural phthalides were obtained. This review provides profiles of the advances in the distribution, chemistry, and biological activities of natural phthalides in 2016-2022.

New neryl esters from Helichrysum italicum (Roth) G. Don (Asteraceae) essential oil

Helichrysum italicum (immortelle) is a dwarf aromatic shrub native to the Mediterranean region. The typical subspecies (italicum) produces an essential oil rich in neryl acetate and characteristic β-diketones, italidiones, highly valued in the perfume industry. As esters are an important group of aroma-active volatiles, herein the composition of the ester fraction of this immortelle chemotype essential oil was studied in detail. Chromatographic separation of Corsican immortelle essential oil enabled the discovery of numerous potentially olfactory-interesting esters of nerol and/or angelic acid, undetectable by direct GC-MS analyses of the unfractioned oil. Four esters of nerol and medium-chain branched fatty acids represent new natural products, while several other esters have a rather restricted occurrence in the Plant Kingdom.

Antimicrobial and α-glucosidase inhibitory activities of chemical constituents from Gardenia aqualla (Rubiaceae)

An aliphatic alkene namely pentapentacontene (4) was isolated for the first time from a natural source, Gardenia aqualla, along with fourteen other compounds including nonacosanol (1), tetratriacontanol (2), octatriacontanol (3), β-sitosterol (5) and stigmasterol (6), daucosanol (7), ursolic acid (8), uvaol (9), 3β,19α,23β,24α-tetrahydroxyurs-12-en-28-oic acid (10), lupenone (11), oleanolic acid (12), vanillin (13), vanillic acid (14) and D-mannitol (15). α-glucosidase inhibitory assay revealed that MeOH and EtOAc extracts of leaves had the best activity with IC₅₀ of 9.65 and 20.03 µg/ml respectively. All the tested compounds showed dose dependent inhibition of α-glucosidase and some of them were found to be comparable to acarbose. Compound 10 was the most potent with IC₅₀ = 1.72 μM. It also showed the most interesting antibacterial activity, against the isolate strain of S. typhi and P. aeruginosa and also exhibited the most significant antifungal activities against all the tested yeasts.

So Uncommon and so Singular, but Underexplored: An Updated Overview on Ethnobotanical Uses, Biological Properties and Phytoconstituents of Sardinian Endemic Plants

The last decades have recorded an increase of plant-based drug discovery processes. Indeed, natural products possess a superior chemical diversity as compared to synthetic ones, leading to a renewal in searching for new therapeutic agents from the plant kingdom. In particular, since the structural variety of natural compounds reflects the biodiversity of their source organisms, regions of the world with high biodiversity and endemism deserve particular interest. In this context, Sardinia Island (Italy), with 290 endemic taxa (12% of the total flora), is expected to provide unique and structurally diverse phytochemicals for drug development. Several research groups built up a large program dedicated to the analysis of Sardinian endemic species, highlighting their peculiar features, both in respect of phytochemical and biological profiles. On this basis, the aim of this review is to provide an up-to-date and comprehensive overview on ethnobotanical uses, biological properties and phytoconstituents of Sardinian endemic plants in order to support their beneficial potential and to provide input for future investigations. We documented 152 articles published from 1965 to June 2020 in which a broad range of biological activities and the identification of previously undescribed compounds have been reported, supporting their great value as sources of therapeutic agents.

Antifungal activity of oils macerates of North Sardinia plants against Candida species isolated from clinical patients with candidiasis

Antibiotic resistance is one of the bigger problem of public health: the rise of multi-drug resistant organisms causes a challenge in the treatment of infective diseases. Anti-Candida resistance to conventional antifungal agents has increased in the last period. Our research was intended to evaluate antimicrobial activity of oil macerate (OM) of Helichrysum microphyllum Cambess. subsp. tyrrhenicum Bacch., Brullo & Giusso and OM of Hypericum perforatum subsp. angustifolium against several clinical strains. The study included 30 patients with candidiasis who had not received any antifungal treatment before they were enrolled. A collection of 30 clinical isolates belonging to 5 different species of Candida spp. was selected for this study. The data obtained showed an interesting activity of both Oil Macerate especially against C. krusei and C. parapsilosis. On the contrary, H. microphyllum Oil Macerate has had a better activity than the H.perforatum especially in relation to C. glabrata and C. krusei.

Identification of Myricetin as an Ebola Virus VP35-Double-Stranded RNA Interaction Inhibitor through a Novel Fluorescence-Based Assay

Ebola virus (EBOV) is a filovirus that causes a severe and rapidly progressing hemorrhagic syndrome; a recent epidemic illustrated the urgent need for novel therapeutic agents because no drugs have been approved for treatment of Ebola virus. A key contribution to the high lethality observed during EBOV outbreaks comes from viral evasion of the host antiviral innate immune response in which viral protein VP35 plays a crucial role, blocking interferon type I production, first by masking the viral double-stranded RNA (dsRNA) and preventing its detection by the pattern recognition receptor RIG-I. Aiming to identify inhibitors of the interaction of VP35 with the viral dsRNA, counteracting the VP35 viral innate immune evasion, we established a new methodology for high-yield recombinant VP35 (rVP35) expression and purification and a novel and robust fluorescence-based rVP35-RNA interaction assay ( Z' factor of 0.69). Taking advantage of such newly established methods, we screened a small library of Sardinian natural extracts, identifying Limonium morisianum as the most potent inhibitor extract. A bioguided fractionation led to the identification of myricetin as the component that can inhibit rVP35-dsRNA interaction with an IC₅₀ value of 2.7 μM. Molecular docking studies showed that myricetin interacts with the highly conserved region of the VP35 RNA binding domain, laying the basis for further structural optimization of potent inhibitors of VP35-dsRNA interaction.

Bioactive Constituents of Juniperus turbinata Guss. from La Maddalena Archipelago

A comprehensive phytochemical study of Juniperus turbinata (Cupressaceae) collected from La Maddalena Archipelago (Sardinia, Italy) is reported. Both the essential oil and the ethanolic extract obtained from the aerial parts were analyzed. The essential oil appears to belong to a new chemotype compared to other Mediterranean juniper accessions, as it was favored by geographic isolation of the isles. It showed a low content of monoterpene hydrocarbons and α-terpineol, ent-manoyl oxide, 1,10-di-epi-cubenol as the major constituents. The ethanolic fraction contained mainly diterpenoids. Among these, 15-formyloxyimbricatolic acid (7) is a new natural product since it has hitherto been obtained only by synthetic route. The phenolic fraction contained biflavonoids: cupressuflavone (9), followed by minor amounts of amentoflavone (10) and hinokiflavone (11). The essential oil and six purified compounds (1 - 4, 8 and 9) were assessed for biological activities, namely antioxidant (assessed by DPPH^· , ABTS^·+ and FRAP methods) and cytotoxic effects towards selected human tumor cell lines (MDA-MB 231, A375 and HCT116 cells). Compound 3 exhibited higher radical scavenging activity against ABTS^·+ radical than the reference Trolox. Noteworthy, compound 8 showed powerful effects towards tumor cell lines, with IC₅₀ values in the range of 0.060 - 0.201 μm, which make it a promising anticancer drug candidate.

Prenylated phloroglucinols from Hypericum scruglii, an endemic species of Sardinia (Italy), as new dual HIV-1 inhibitors effective on HIV-1 replication

In a search for new potential multitarget anti-HIV compounds from natural products, we have identified in Hypericum scruglii, an endemic and exclusive species of Sardinia (Italy), a potent plant lead. The phytochemical study of the hydroalcoholic extract obtained from its leaves led to the isolation of its most abundant secondary metabolites, belonging to different chemical classes. In particular, three phloroglucinols derivatives were identified, confirming their significance as chemotaxonomic markers of the Hypericum genus. Among them, the 3-(13-hydroxygeranyl)-1-(2'-methylbutanoyl)phloroglucinol was reported here for the first time. All six isolated compounds have been evaluated firstly for the inhibition of both Human Immunodeficiency Virus type 1 (HIV-1) Reverse Transcriptase (RT)-associated DNA Polymerase (RDDP) and Ribonuclease H (RNase H) activities, for the inhibition of HIV-1 integrase (IN) in biochemical assays, and also for their effect on viral replication. Among the isolated metabolites, three phloroglucinol derivatives and quercitrin were effective on both RT-associated RDDP and RNase H activities in biochemical assays. The same active compounds affected also HIV-1 IN strand transfer function, suggesting the involvement of the RNase H active site. Furthermore, phloroglucinols compounds, included the newly identified compound, were able to inhibit the HIV-1 replication in cell based assays.

Dual HIV-1 reverse transcriptase and integrase inhibitors from Limonium morisianum Arrigoni, an endemic species of Sardinia (Italy)

During our search for potential templates of HIV-1 reverse transcriptase (RT) and integrase (IN) dual inhibitors, the methanolic extract obtained from aerial parts of Limonium morisianum was investigated. Repeated bioassay-guided chromatographic purifications led to the isolation of the following secondary metabolites: myricetin, myricetin 3-O-rutinoside, myricetin-3-O-(6″-O-galloyl)-β-d-galactopyranoside, (-)-epigallocatechin 3-O-gallate, tryptamine, ferulic and phloretic acids. The isolated compounds were tested on both HIV-1 RT-associated RNase H and IN activities. Interestingly, (-)-epigallocatechin-3-O-gallate and myricetin-3-O-(6″-O-galloyl)-β-d-galactopyranoside potently inhibited both enzyme activities with IC₅₀ values ranging from 0.21 to 10.9 μM. Differently, tryptamine and ferulic acid exhibited a significant inhibition only on the IN strand transfer reaction, showing a selectivity for this viral enzyme. Taken together these results strongly support the potential of this plant as a valuable anti HIV-1 drugs source worthy of further investigations.

New Coumarinyl Ethers in Daphne oleoides Schreb. Collected from Sardinia Island

The phytochemical analysis of the ethanolic extract obtained from D. oleoides collected from Sardinia Island allowed the isolation of several new constituents for the species (3, 8, and 9) together with two new coumarinyl ethers (1 and 2) besides the chemotaxonomic markers of the Daphne genus (4 - 7 and 10) which are also known to possess interesting biological activities. The structure of the new compounds were elucidated by extensive spectroscopic and spectrometric analyses. The identification of these compounds gives an experimental evidence of the variability in the secondary metabolites pattern owned by populations growing in restricted area in respect to populations not confined by geographical barrier.