Meroterpenoids from a Medicinal Fungus Antrodia cinnamomea

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Chemical investigations and cytotoxic effects of metabolites from Antrodia camphorata against human hepatocellular carcinoma cells

Antrodia camphorata is used as a medicinal fungus in Taiwan to treat fatigue, food intoxication, and enhance liver function. Here we identified fermented metabolic components from the mycelium of A. camphorata KH37 and explored their anti-hepatoma potentials with study models of human hepatoblastoma cell lines. Bioassay-guided fractionation of the solid fermentation powder of A. camphorata KH37 led to the isolation of one new quinonol, antroquinonol Z (1), and nine known compounds (2-10). Treatment with 10 μM antrocamols LT1 (2) or LT3 (3) reduced cell viability of HepG2 and Huh-7 cells to about 60% in 48 hours. Antroquinonol Z (1) exhibited mild cytotoxicity against Huh-7 cells in 48 and 72 hours. Interestingly, two fractions showed cytotoxicity in HepG2 and Huh-7 cells, even better than compounds isolated from these fractions. The significant cytotoxicity of partially purified samples from A. camphorata KH37 exhibited a potential for developing alternative or complementary therapeutics against hepatoma.

Two New Compounds from the Fungus Xylaria nigripes

In the process of discovering more neural-system-related bioactive compounds from Xylaria nigripes, xylariamino acid A (1), a new amino acid derivative, and a new isovaleric acid phenethyl ester (2) were isolated and identified. Their structures and absolute configurations were determined by analyses of IR, HRESIMS, NMR spectroscopic data, and gauge-independent atomic orbital (GIAO) NMR calculation, as well as electronic circular dichroism (ECD) calculation. The isolated compounds were evaluated for their neuroprotective effects against damage to PC12 cells by oxygen and glucose deprivation (OGD). Compounds 1 and 2 can increase the viability of OGD-induced PC12 cells at all tested concentrations. Moreover, compound 2 (1 μmol L^-1) can significantly reduce the percentage of apoptotic cells.

Biological activities of meroterpenoids isolated from different sources

Meroterpenoids are natural products synthesized by unicellular organisms such as bacteria and multicellular organisms such as fungi, plants, and animals, including those of marine origin. Structurally, these compounds exhibit a wide diversity depending upon the origin and the biosynthetic pathway they emerge from. This diversity in structural features imparts a wide spectrum of biological activity to meroterpenoids. Based on the biosynthetic pathway of origin, these compounds are either polyketide-terpenoids or non-polyketide terpenoids. The recent surge of interest in meroterpenoids has led to a systematic screening of these compounds for many biological actions. Different meroterpenoids have been recorded for a broad range of operations, such as anti-cholinesterase, COX-2 inhibitory, anti-leishmanial, anti-diabetic, anti-oxidative, anti-inflammatory, anti-neoplastic, anti-bacterial, antimalarial, anti-viral, anti-obesity, and insecticidal activity. Meroterpenoids also possess inhibitory activity against the expression of nitric oxide, TNF- α, and other inflammatory mediators. These compounds also show renal protective, cardioprotective, and neuroprotective activities. The present review includes literature from 1999 to date and discusses 590 biologically active meroterpenoids, of which 231 are from fungal sources, 212 are from various species of plants, and 147 are from marine sources such as algae and sponges.

Two New Picoline-Derived Meroterpenoids with Anti-Acetylcholinesterase Activity from Ascidian-Derived Fungus Amphichorda felina

Amphichoterpenoids D (1) and E (2), two new picoline-derived meroterpenoids with a rare 6/6/6 tricyclic pyrano[3,2-c]pyridinyl-γ-pyranone scaffold, were isolated from the ascidian-derived fungus Amphichorda felina SYSU-MS7908. Their structures, including the absolute configurations, were established by extensive spectroscopic methods (1D and 2D NMR and high-resolution mass spectrometry) and ECD calculations. Compounds 1 and 2 showed anti-acetylcholinesterase (anti-AChE) activities with IC₅₀ values of 12.5 μM and 11.6 μM, respectively. The binding interactions between 1, 2, and AChE were investigated using molecular docking analyses.

Solid-state-cultured mycelium of Antrodia camphorata exerts potential neuroprotective activities against 6-hydroxydopamine-induced toxicity in PC12 cells

Antrodia camphorata (A. camphorata) is an edible fungus containing various bioactive compounds generally used for health benefits. This study aimed to explore the potential neuroprotective activities of solid-state-cultured mycelium of A. camphorata (SCMAC) against Parkinson's disease (PD), as well as the underlying mechanism using an in vitro 6-hydroxydopamine (6-OHDA)-induced PC12 cell model. The results showed that SCMAC extracts alleviated cell toxicity induced by 6-OHDA and the loss of dopaminergic neurons, which was confirmed by the increase of cell viabilities, inhibition of cell apoptosis, the upregulation of tyrosine hydroxylase (TH) and dopamine transporter (DAT) levels and the downregulation of α-Synuclein level. After purification, 11 compounds were identified by the NMR technique, including a quinone, four phenolic acid derivatives, three ubiquinone derivatives, two alkaloids, and a triterpenoid. The present study suggests that SCMAC could be an attractive candidate for the prevention or treatment of PD. PRACTICAL APPLICATIONS: Parkinson's disease seriously affects the lifetime and quality of the elder population for a long history. Long-term consumption of L-DOPA will result in side effects, such as developing abnormal involuntary movements called dyskinesia. This study showed that natural SCMAC extracts could be a potential therapeutic agent for the treatment of neurodegenerative disorder.

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

Chemical constituents from the dish-cultured Antrodia camphorata and their cytotoxic activities

One new meroterpenoid, antroquinonol Y (1), a new ergostane-type sterol, antcamphin Y (2), and a new ergostane-type triterpenoid, antcamphin Z (3), together with 10 known ones (4-13), were isolated from the dish-cultured fungus Antrodia camphorata. Their structures were characterized by extensive NMR and HRESIMS data analyses. The absolute configurations were elucidated by experimental and calculated electronic circular dichroism (ECD) spectral analyses and chemical semi-synthesis. Compounds 1, 3, and 5 exhibited potent inhibitory activities against four human cancer cell lines (U251, HL60, SW480, and A549 cells) with IC₅₀ values of 4.6 to 11.7 μM.

A Mechanistic Review on Medicinal Mushrooms-Derived Bioactive Compounds: Potential Mycotherapy Candidates for Alleviating Neurological Disorders

According to the World Health Organization, neurological and neurodegenerative diseases are highly debilitating and pose the greatest threats to public health. Diseases of the nervous system are caused by a particular pathological process that negatively affects the central and peripheral nervous systems. These diseases also lead to the loss of neuronal cell function, which causes alterations in the nervous system structure, resulting in the degeneration or death of nerve cells throughout the body. This causes problems with movement (ataxia) and mental dysfunction (dementia), both of which are commonly observed symptoms in Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. Medicinal mushrooms are higher fungi with nutraceutical properties and are low in calories and fat. They are also a rich source of nutrients and bioactive compounds such as carbohydrates, proteins, fibers, and vitamins that have been used in the treatment of many ailments. Medicinal mushrooms such as Pleurotus giganteus, Ganoderma lucidium, and Hericium erinaceus are commonly produced worldwide for use as health supplements and medicine. Medicinal mushrooms and their extracts have a large number of bioactive compounds, such as polysaccharide β-glucan, or polysaccharide-protein complexes, like lectins, lactones, terpenoids, alkaloids, antibiotics, and metal-chelating agents. This review will focus on the role of the medicinal properties of different medicinal mushrooms that contain bioactive compounds with a protective effect against neuronal dysfunction. This information will facilitate the development of drugs against neurodegenerative diseases.

Meroterpenoids produced by fungi: Occurrence, structural diversity, biological activities, and their molecular targets

Meroterpenoids are partially derived from the terpenoids, distributing widely in the plants, animals and fungi. The complex structures and diverse bioactivities of meroterpenoids have attracted more attention for chemists and pharmacologists. Since the first review summarized by Geris in 2009, there are absent of systematic reviews reported about meroterpenoids from the higher and lower fungi up to now. In the past decades, myriads of meroterpenoids were discovered, and it is necessary to summarize these meroterpenoids about their unique structures and promising bioactivities. In this review, we use a new classification method based on the non-terpene precursors, and also highlight the structural features, bioactivity of natural meroterpenoids from the higher and lower fungi covering the period of September 2008 to February 2020. A total of 709 compounds were discussed and cited the 182 references. Meanwhile, we also primarily summarize their occurrence, structural diversity, biological activities, and molecular targets.

Terpenoids from the medicinal mushroom Antrodia camphorata: chemistry and medicinal potential

Covering: up to February 2020Antrodia camphorata is a medicinal mushroom endemic to Taiwan for the treatment of intoxication, liver injury, cancer, and inflammation. Owing to its rare occurrence and potent pharmacological activities, efforts have been devoted to identify its bioactive constituents, especially terpenoids. Since 1995, a total of 162 terpenoids including triterpenoids, meroterpenoids, sesquiterpenoids, diterpenoids, and steroids have been characterized. The ergostane-type triterpenoids (antcins) and meroterpenoids (antroquinonols) are characteristic constituents of A. camphorata. The terpenoids show anti-cancer, hepatoprotective, anti-inflammatory, anti-diabetic, and neuroprotective activities. This review summarizes the research progress on terpenoids in A. camphorata during 1995-2020, including structural diversity, resources, biosynthesis, pharmacological activities, metabolism, and toxicity. The medicinal potential of the terpenoids is also discussed.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

4-Hydroxybenzoic acid serves as an endogenous ring precursor for antroquinonol biosynthesis in Antrodia cinnamomea

Antrodia cinnamomea, an endemic fungus species of Taiwan, has long been used as a luxurious dietary supplement to enhance liver functions and as a remedy for various cancers. Antroquinonol (AQ), identified from the mycelium of A. cinnamomea, is currently in phase II clinical trials in the USA and Taiwan for the treatment of non-small-cell lung cancer. In the previous studies, we have demonstrated that AQ and 4-acetylantroquinonol B (4-AAQB) utilize orsellinic acid, via polyketide pathway, as the ring precursor, and their biosynthetic sequences are similar to those of coenzyme Q. In order to test 4-hydroxybenzoic acid (4-HBA), synthesized via shikimate pathway, is the ring precursor of AQ analogs, the strategy of metabolic labeling with stable isotopes was applied in this study. Here we have confirmed that 4-HBA serves as the ring precursor for AQ but not a precursor of 4-AAQB. Experimental results indicated that A. cinnamomea preferentially utilizes endogenous 4-HBA via shikimate pathway for AQ biosynthesis. Exogenous tyrosine and phenylalanine can be utilized for AQ biosynthesis when shikimate pathway is blocked by glyphosate. The benzoquinone ring of 4-AAQB is synthesized only via polyketide pathway, but that of AQ is synthesized via both polyketide pathway and shikimate pathway. The precursor-products relationships diagram of AQ and 4-AAQB in A. cinnamomea are proposed based on the experimental findings.