Cytotoxic diterpenes from the rhizomes of Hedychium coronarium

Labdane-type diterpenoids and sesquiterpenes from Curcuma aromatica and their nitric oxide inhibitory activity in lipopolysaccharide-stimulated RAW264.7 macrophages

One new labdane-type diterpenoid, 3β,15-dihydroxylabda-8(17),12E-dien-16,15-olide (1) named curcumatin and twelve known compounds, coronarin D (2), isocoronarin D (3), (E)-labda-8(17),12-diene-15,16-dial (4), zerumin A (5), (E)-labda-8(17),12-dien-15,16-dioic acid (6), furanodiene (7), linderazulene (8), zedoarol (9), zedoarondiol (10), germacrone-1,10-epoxide (11), germacrone-4,5-epoxide (12), and zingiberenol (13) were isolated from the ethanol extract of the roots of Curcuma aromatica Salisb. Their structures were elucidated by 1D-, 2D-NMR spectroscopic analysis, HR-ESI-MS, and comparing with the NMR data reported in the literature. Compounds 2, 5, and 13 significantly inhibited the nitric oxide production effect in LPS-stimulated RAW 264.7 macrophages with IC50 values of 8.8 ± 1.7, 4.0 ± 0.9, and 6.2 ± 0.4 µM, respectively.

A Comprehensive Review on Pharmacologically Active Phyto-Constituents from Hedychium species

In this review, we describe and discuss the phytoconstituents present in Hedychium species and emphasize their potential as drug candidates. Though they are widely validated in vitro and in vivo models, to date, no efforts have been made to compile in a single review all the pharmacologically active phytoconstituents from Hedychium species, and their pharmacological and toxicity profile. In this study, we present a reinvestigation of the chemical constituents present in Hedychium species obtained from the essential oil and solvent extraction of the flowers, leaves and rhizomes under consideration. Key databases such as PubMed, Science Direct, Scopus, and Google Scholar amongst others were probed for a systematic search using keywords to retrieve relevant publications on this plant. An exhaustive electronic survey of the related literature on Hedychium species resulted in around 200 articles. Articles published between the years 1975-2021 were included. The studies conducted on either crude extracts, solvent fractions or isolated pure compounds from Hedychium species reported with a varied range of biological effects such as anti-inflammatory, analgesic, antidiabetic, potentially anti-asthmatic, and cytotoxic, among other related activities of the chemical constituents present in its essential oil and solvent extract deployed in this review. Traditional and herbal medication around the world that uses different parts of Hedychium species were considered for anti-inflammatory, skincare, analgesic, anti-asthmatic, anti-diabetic, antidotal uses, among others. These uses support the idea that chemical constituents obtained from solvent extraction may also exert the same action individually or in a synergistic manner. The review concluded that there is scope for computation and biological study to find out possible new targets for strengthening the potency and selectivity of the relevant compounds, and to find a commercial method for extraction of active pharmaceutical ingredients.

Advances on Natural Abietane, Labdane and Clerodane Diterpenes as Anti-Cancer Agents: Sources and Mechanisms of Action

Extensive research over the past decades has identified numerous phytochemicals that could represent an important source of anti-cancer compounds. There is an immediate need for less toxic and more effective preventive and therapeutic strategies for the treatment of cancer. Natural compounds are considered suitable candidates for the development of new anti-cancer drugs due to their pleiotropic actions on target events with multiple manners. This comprehensive review highlighted the most relevant findings achieved in the screening of phytochemicals for anticancer drug development, particularly focused on a promising class of phytochemicals such as diterpenes with abietane, clerodane, and labdane skeleton. The chemical structure of these compounds, their main natural sources, and mechanisms of action were critically discussed.

Coronarin D, a Metabolite from the Wild Turmeric, Curcuma aromatica, Promotes the Differentiation of Neural Stem Cells into Astrocytes

Plants in the genus Curcuma have been widely used as traditional medicines in Asian countries. These plants contain bioactive compounds with neuroprotective properties or activities that increase neural stem cells (NSCs) and neurons. However, bioactive components in Curcuma that promote the differentiation of NSCs into astrocytes have not yet been reported. Here, the effects of Curcuma extracts on the in vitro differentiation of embryonic stem-cell-derived NSCs were evaluated. The extract of the wild turmeric, Curcuma aromatica, strongly promoted the differentiation of NSCs into astrocytes. Bioassay-guided isolation yielded coronarins C (1) and D (2), as well as (E)-labda-8(17),12-diene-15,16-dial (3) as the bioactive compounds. Coronarin D (2) markedly promoted the differentiation of NSCs into astrocytes up to approximately 4 times (3.64 ± 0.48) and increased the expression level of GFAP at the mRNA and protein level, while compounds 1 and 3 exhibited only weak effects, suggesting that the 15-hydroxy-Δ¹²-γ-lactone moiety is important for bioactivity. Moreover, compound 2 increased the number of pSTAT3-positive cells, suggesting that compound 2 promoted astrocytic differentiation through JAK/STAT signaling pathway.

Antiproliferative labdane diterpenes from the rhizomes of Hedychium flavescens Carey ex Roscoe

Antiproliferative activity was confirmed in the various extracts of rhizomes of Hedychium flavescens (Zingiberaceae). The phytochemical investigation of the rhizomes of Hedychium flavescens led to the isolation of four labdane diterpenes. Their structures were established as coronarin E (1), C-14 epimers of isocoronarin D (2), C-15 epimers of coronarin D methyl ether (3) and isocoronarin D (4). The structure of the compounds was identified based on spectroscopic analysis and on comparison with literature reports. All these compounds were assessed for their in vitro cytotoxicity against human lung adenocarcinoma (A549) cell line and showed significant cytotoxicity as reflected in IC₅₀ value, that is, 0.52, 0.59, 0.68 and 1.22 μM compared with the control doxorubicin (IC₅₀ 0.92 μM). Moreover, all the compounds were nontoxic towards the normal lung fibroblast (WI-38) cells. The chemo-profiling and cytotoxicity study of Hedychium flavescens is reported for the first time.

Coronarin K and L: Two Novel Labdane Diterpenes From Roscoea purpurea: An Ayurvedic Crude Drug

The main objective of cancer treatment with chemotherapy is to kill the cancerous cells without affecting the healthy normal cells. In the present study, bioactivity-guided purification of the n-chloroform soluble fraction from the methanol extract of Roscoea purpurea resulted in the identification of two new labdane diterpenes: coronarin K (1) and coronarin L (2), along with eight known compounds, coronarin A (3), bisdemethoxycurcumin (4), kaempferol 3-O-methyl ether (5), kaempferol (6), fenozan acid (7), 3-(3-methoxy,4-hydroxyphenyl)-2-propenoic acid ferulic acid (8), caffeic acid (9), and gallic acid (10). The structural identification of new compounds (1 and 2) were determined by detailed analysis of 1D (¹H and ¹³C) and 2D NMR (COSY, HSQC, and HMBC) spectroscopic data. The relative configurations of 1 and 2 were determined with the help of NOESY correlations and comparison of optical rotations with known labdane diterpenes, with established stereochemistry, while structure of known compounds was established by direct comparison of their NMR data with those reported in the literature. This is the first report of isolation of this labdane diterpenes and phenolic classes of secondary metabolites in R. purpurea. In the preliminary screening, the methanol extract and its fractions were tested for the cytotoxic activity against a panel of four cancer cell lines (A549, HCT-116, Bxpc-3, and MCF-7); extract and its chloroform fraction were found to be active against the lung cancer cell line, A-549, with IC₅₀ value <25 μg/ml. Owing to the notable cytotoxic activity of the chloroform fraction, the compounds (1-5) were screened for their cytotoxicity against all the cell lines by MTT assay. Coronarin K, 1 showed significant cytotoxic potential against lung cancer cell lines (A-549), with IC₅₀ value of 13.49 μM, while other compounds did not show activity below 22 μM.

Antiprotozoal and Antitumor Activity of Natural Polycyclic Endoperoxides: Origin, Structures and Biological Activity

Polycyclic endoperoxides are rare natural metabolites found and isolated in plants, fungi, and marine invertebrates. The purpose of this review is a comparative analysis of the pharmacological potential of these natural products. According to PASS (Prediction of Activity Spectra for Substances) estimates, they are more likely to exhibit antiprotozoal and antitumor properties. Some of them are now widely used in clinical medicine. All polycyclic endoperoxides presented in this article demonstrate antiprotozoal activity and can be divided into three groups. The third group includes endoperoxides, which show weak antiprotozoal activity with a reliability of up to 70%, and this group includes only 1.1% of metabolites. The second group includes the largest number of endoperoxides, which are 65% and show average antiprotozoal activity with a confidence level of 70 to 90%. Lastly, the third group includes endoperoxides, which are 33.9% and show strong antiprotozoal activity with a confidence level of 90 to 99.6%. Interestingly, artemisinin and its analogs show strong antiprotozoal activity with 79 to 99.6% confidence against obligate intracellular parasites which belong to the genera Plasmodium, Toxoplasma, Leishmania, and Coccidia. In addition to antiprotozoal activities, polycyclic endoperoxides show antitumor activity in the proportion: 4.6% show weak activity with a reliability of up to 70%, 65.6% show an average activity with a reliability of 70 to 90%, and 29.8% show strong activity with a reliability of 90 to 98.3%. It should also be noted that some polycyclic endoperoxides, in addition to antiprotozoal and antitumor properties, show other strong activities with a confidence level of 90 to 97%. These include antifungal activity against the genera Aspergillus, Candida, and Cryptococcus, as well as anti-inflammatory activity. This review provides insights on further utilization of polycyclic endoperoxides by medicinal chemists, pharmacologists, and the pharmaceutical industry.

Bioactive Compounds from Medicinal Plants in Myanmar

Myanmar is a country with rich natural resources and of these, medicinal plants play a vital role in the primary health care of its population. The people of Myanmar have used their own system of traditional medicine inclusive of the use of medicinal plants for 2000 years. However, systematic and scientific studies have only recently begun to be reported. Researchers from Japan, Germany, and Korea have collaborated with researchers in Myanmar on medicinal plants since 2000. During the past two decades, over 50 publications have been published in peer-reviewed journals. Altogether, 433 phytoconstituents, including 147 new and 286 known compounds from 26 plant species consisting of 29 samples native to Myanmar, have been collated. In this contribution, phytochemical and biological investigations of these plants, including information on traditional knowledge are compiled and discussed.

Clerodane Diterpenoids from Callicarpa hypoleucophylla and Their Anti-Inflammatory Activity

Plants of the genus Callicarpa are known to possess several medicinal effects. The constituents of the Taiwan endemic plant Callicarpa hypoleucophylla have never been studied. Therefore, C. hypoleucophylla was selected for our phytochemical investigation. Two new clerodane-type diterpenoids, named callihypolins A (1) and B (2), along with seven known compounds were isolated from the leaves and twigs of the Lamiaceae plant C. hypoleucophylla and then characterized. The structures of compounds 1 and 2 were elucidated by spectroscopic data analysis, specifically, two-dimension nuclear magnetic resonance (NMR). The anti-inflammatory activity of compounds 1-9 based on the suppression of superoxide anion generation and elastase release was evaluated. Among the isolates, compounds 2-4 showed anti-inflammatory activity (9.52-32.48% inhibition at the concentration 10 μm) by suppressing superoxide anion generation and elastase release. Our findings not only expand the description of the structural diversity of the compounds present in plants of the genus Callicarpa but also highlight the possibility of developing anti-inflammatory agents from Callicarpa endemic species.

Coronarin D Induces Apoptotic Cell Death and Cell Cycle Arrest in Human Glioblastoma Cell Line

Glioblastoma (GBM) is the most frequent and highest-grade brain tumor in adults. The prognosis is still poor despite the use of combined therapy involving maximal surgical resection, radiotherapy, and chemotherapy. The development of more efficient drugs without noticeable side effects is urgent. Coronarin D is a diterpene obtained from the rhizome extract of Hedychium coronarium, classified as a labdane with several biological activities, principally anticancer potential. The aim of the present study was to determine the anti-cancer properties of Coronarin D in the glioblastoma cell line and further elucidate the underlying molecular mechanisms. Coronarin D potently suppressed cell viability in glioblastoma U-251 cell line, and also induced G1 arrest by reducing p21 protein and histone H2AX phosphorylation, leading to DNA damage and apoptosis. Further studies showed that Coronarin D increased the production of reactive oxygen species, lead to mitochondrial membrane potential depolarization, and subsequently activated caspases and ERK phosphorylation, major mechanisms involved in apoptosis. To our knowledge, this is the first analysis referring to this compound on the glioma cell line. These findings highlight the antiproliferative activity of Coronarin D against glioblastoma cell line U-251 and provide a basis for further investigation on its antineoplastic activity on brain cancer.

Coronarin D induces human oral cancer cell apoptosis though upregulate JNK1/2 signaling pathway

The incidence of oral cancer is increasing all over the world, with rates particularly high in Southeast Asian countries, such as Taiwan. Coronarin D (CD) has been confirmed to have anti-inflammatory, anti-bacterial effects, and anti-apoptotic effects in human hepatocellular carcinoma and nasopharyngeal carcinoma. The purpose of this study is to explore whether CD has a suppression effect on oral cancer cells and the mechanisms involved. The results of our study revealed the significantly decreased cancer cell viability and increased activation of apoptosis via increased loss of mitochondrial membrane potential, increased death receptors, leading to the activation of caspase-8, -9, -3. Moreover, the rate of apoptosis of cells treated with CD plus JNK inhibitors was decreased compared to CD-treated cells. This is the first study to demonstrate that CD induces apoptosis in human oral cancer cells and can be expected to be a promising anticancer agent for oral cancer treatment.

Synthesis of (+)-Coronarin E, (-)-7-epi-Coronarin a and (+)-15, 16-Epoxy-8(17), 13(16), 14-Labdatriene from (+)-Manool

An efficient method for the synthesis of (+)-coronarin E 1, (+)- epi-coronarin A 2 and (+)-15, 16-epoxy-8(17), 13(16), 14-labdatriene 3 via the homodrimane 9, obtained in four steps from (+)-manool 5, is described.

Facile Access to Labdane-type Diterpenes: Synthesis of Coronarin C, Zerumin B, Labda-8(17), 13(14)-dien-15,16-olide and derivatives from (+)-manool

A practical method for the synthesis of optically active labdane-type diterpenes from (+)-manool 8, is described. We prepared the natural labdane-type diterpene 5 via key intermediate peroxide 9 and coronarin C 1, compound 8 and zerumin B 6 via a furan photosensitised oxygenation reactions.

Labdane diterpenoids from Curcuma amada rhizomes collected in Myanmar and their antiproliferative activities

Four new labdane diterpenoids, 12β-hydroxy-15-norlabda-8(17),13(14)-dien-16-oic acid (1), (E)-15-ethoxy-15-methoxylabda-8(17),12-dien-16-al (2), (E)-15α-ethoxy-14α-hydroxylabda-8(17),12-dien-16-olide (3), and 15-ethoxy-12β-hydroxylabda-8(17),13(14)-dien-16,15-olide (4) were isolated from the methanol extract of Curcuma amada rhizomes collected in Myanmar, together with 13 known analogs. Their structures were elucidated by extensive spectroscopic techniques. All of the isolates were evaluated for their antiproliferative activities against a small panel of five different human cancer cell lines (A549, human lung cancer; HeLa, human cervical cancer; MCF7, human breast cancer; PANC-1 and PSN-1, human pancreatic cancer). Among the isolates, compounds 2-4, 7, 8, 12, and 17 showed mild antiproliferative activities with IC₅₀ values ranging from 19.7 to 96.1μM. (E)-14-Hydroxy-15-norlabda-8(17),12-dien-16-al (11) exhibited strong antiproliferative activities selectively against HeLa, PANC-1, and PSN-1 cells, with IC₅₀ values of 5.88, 1.00, and 3.98μM, respectively. These potencies were comparable to those of the positive control, 5-fluorouracil.

Vitepyrroloids A-D, 2-Cyanopyrrole-Containing Labdane Diterpenoid Alkaloids from the Leaves of Vitex trifolia

Vitepyrroloids A-D (1-4), four new 2-cyano-substituted pyrrole-ring-containing labdane diterpenoids, were isolated from the leaves of Vitex trifolia. Their structures were elucidated based on spectroscopic data analysis. The absolute configuration of compound 1 was determined by X-ray diffraction. Compounds 1-4 are unprecedented labdane diterpenoids featuring a 2-cyano-substituted pyrrole ring. Compound 1 showed cytotoxic activity against a human nasopharyngeal carcinoma cell line (CNE1) with an IC₅₀ value of 8.7 μM.

An overview of chemical constituents from Alpinia species in the last six decades

Alpinia species is one of the most important genera of the Zingiberaceae family. Up to 2015, 544 compounds with various bioactivities were isolated, the major components are diarylheptanoids (143) and sesquiterpenoids (132).

Cytotoxic Labdane Diterpenes from Hedychium ellipticum Buch.-Ham. ex Sm

In order to reveal the constituents and their biological activities, we carried out a phytochemical study on Hedychium ellipticum Buch.-Ham. ex Sm. (Zingiberaceae). Ten labdane diterpenoids (1–10) were isolated from the rhizomes of H. ellipticum for the first time. Their structures were identified on the basis of spectroscopic analyses including two-dimensional NMR and comparison with literature data. All of these compounds were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis and cytotoxicity against KB, MCF7, NCI-H187 and Vero cells. The result showed that compounds 1 and 7 exhibited moderate activity against Mycobacterium tuberculosis and compounds 4, 6 and 7 displayed remarkable cytotoxic activity. This is the first report on the presence of all compounds in H. ellipticum and the first time that their structure activity relationship has been discussed.

Phytochemistry and pharmacology of ornamental gingers, Hedychium coronarium and Alpinia purpurata: a review

In this review, the phytochemistry and pharmacology of two ornamental gingers, Hedychium coronarium (butterfly ginger) and Alpinia purpurata (red ginger), are updated, and their botany and uses are described. Flowers of H. coronarium are large, showy, white, yellow or white with a yellow centre and highly fragrant. Inflorescences of A. purpurata are erect spikes with attractive red or pink bracts. Phytochemical investigations on the rhizomes of H. coronarium generated research interest globally. This resulted in the isolation of 53 labdane-type diterpenes, with little work done on the leaves and flowers. Pharmacological properties of H. coronarium included antioxidant, antibacterial, antifungal, cytotoxic, chemopreventive, anti-allergic, larvicidal, anthelminthic, analgesic, anti-inflammatory, anti-urolithiatic, anti-angiogenic, neuro-pharmacological, fibrinogenolytic, coagulant and hepatoprotective activities. On the contrary, little is known on the phytochemistry of A. purpurata with pharmacological properties of antioxidant, antibacterial, larvicidal, cytotoxic and vasodilator activities reported in the leaves and rhizomes. There is much disparity in terms of research effort within and between these two ornamental gingers.

Tetrahydropyran- and tetrahydrofuran-containing diarylheptanoids from Hedychium coronarium rhizomes

Seven new diarylheptanoids (1-7) were isolated from the n-BuOH-soluble fraction of the rhizome of Hedychium coronarium. Hedycoropyrans A-C (1-3) contain a tetrahydropyran moiety, while hedycorofurans A-D (4-7) contain a tetrahydrofuran moiety, belonging to a rare structural class of diarylheptanoids. Their structures including stereochemistry were elucidated on the basis of 1D and 2D NMR and ECD spectroscopic analyses and HRESIMS data of the parent compounds and the isopropylidene derivatives of 4 and 7.

Phytochemical profiling of Curcuma kwangsiensis rhizome extract, and identification of labdane diterpenoids as positive GABAA receptor modulators

An ethyl acetate extract of Curcuma kwangsiensis S.G. Lee & C.F. Liang (Zingiberaceae) rhizomes (100 μg/ml) enhanced the GABA-induced chloride current (IGABA) through GABAA receptors of the α1β2γ2S subtype by 79.0±7.0%. Potentiation of IGABA was measured using the two-microelectrode voltage-clamp technique and Xenopus laevis oocytes. HPLC-based activity profiling of the crude extract led to the identification of 11 structurally related labdane diterpenoids, including four new compounds. Structure elucidation was achieved by comprehensive analysis of on-line (LC-PDA-ESI-TOF-MS) and off-line (microprobe 1D and 2D NMR) spectroscopic data. The absolute configuration of the compounds was established by comparison of experimental and calculated ECD spectra. Labdane diterpenes represent a new class of plant secondary metabolites eliciting positive GABAA receptor modulation. The highest efficiency was observed for zerumin A (maximum potentiation of IGABA by 309.4±35.6%, and EC50 of 24.9±8.8 μM).

New Labdane-type diterpenoids and anti-inflammatory constituents from Hedychium coronarium

Four new labdane-type diterpenoids: hedychicoronarin (1), peroxycoronarin D (2), 7β-hydroxycalcaratarin A (3), and (E)-7β-hydroxy-6-oxo-labda-8(17),12-diene-15,16-dial (4), have been isolated from the rhizomes of Hedychium coronarium, together with 13 known compounds (5–17). The structures of these new compounds were determined through spectroscopic and MS analyses. Compounds 3, 5, 6, and 10 exhibited inhibition (IC₅₀ values ≤4.52 μg/mL) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 3–6, 10, and 11 inhibited fMLP/CB-induced elastase release with IC₅₀ values ≤6.17 μg/mL.

Use of (+)-manool in the Synthesis of Natural Products. Part II. Diterpenes and Relatives

The syntheses of several kind of natural product skeletal including as ring C aromatic diterpenes, labdane, diterpenoid, purines and tricarbocyclic diterpenes from the diterpenoid (+)-manool are described in this review.

Coronarin D Conjugated to Methylene Homologues of Chlorambucil: Synthesis and Evaluation of their Cytotoxicity

Methylene homologues of chlorambucil were synthesised and conjugated to the labdane diterpene coronarin D. The products were evaluated for their in vitro cytotoxicity, and were found to exhibit selective activity against MOLT-3 cell line. Two homologues of chlorambucil showed a comparable cytotoxic effect to their parent. However, as compared with the non-derivatised chlorambucil and its homologues, their conjugation with coronarin D through ester linkage did not enhance in vitro cytotoxicity against the tested cancer cell lines.