Inhibitory effects of phylligenin and quebrachitol isolated from Mitrephora vulpina on platelet activating factor receptor binding and platelet aggregation

Synthesis and evaluation of L-quebrachitol derivatives against platelet aggregation

Thrombosis plays an important role in the occurrence and development of cardiovascular and cerebrovascular diseases that contribute to high mortality and morbidity in patients. L-(-)-Quebrachitol (QCT), a natural product, was first isolated from quebracho bark. It can inhibit PAF receptor and decrease gastric damage induced by indomethacin, as a drug against platelet aggregation. Here, five QCT derivatives were synthesized and investigated for their inhibitory effects on platelet aggregation. Among them, compound 3a showed anticoagulant effects comparable to aspirin, while compound 4b showed dose-independent inhibitory activities in rats that were stronger than aspirin.

A comprehensive review on pharmacological, toxicity, and pharmacokinetic properties of phillygenin: Current landscape and future perspectives

Forsythiae Fructus is a traditional Chinese medicine frequently in clinics. It is extensive in the treatment of various inflammation-related diseases and is renowned as 'the holy medicine of sores'. Phillygenin (C21H24O6, PHI) is a component of lignan that has been extracted from Forsythiae Fructus and exhibits notable biological activity. Modern pharmacological studies have confirmed that PHI demonstrates significant activities in the treatment of various diseases, including inflammatory diseases, liver diseases, cancer, bacterial infection and virus infection. Therefore, this review comprehensively summarizes the pharmacological effects of PHI up to June 2023 by searching PubMed, Web of Science, Science Direct, CNKI, and SciFinder databases. According to the data, PHI shows remarkable anti-inflammatory, antioxidant, hepatoprotective, antitumour, antibacterial, antiviral, immunoregulatory, analgesic, antihypertensive and vasodilatory activities. More importantly, NF-κB, MAPK, PI3K/AKT, P2X7R/NLRP3, Nrf2-ARE, JAK/STAT, Ca2+-calcineurin-TFEB, TGF-β/Smads, Notch1 and AMPK/ERK/NF-κB signaling pathways are considered as important molecular targets for PHI to exert these pharmacological activities. Studies of its toxicity and pharmacokinetic properties have shown that PHI has very low toxicity, incomplete absorption in vivo and low oral bioavailability. In addition, the physico-chemical properties, new formulations, derivatives and existing challenges and prospects of PHI are also reviewed and discussed in this paper, aiming to provide direction and rationale for the further development and clinical application of PHI.

Mechanism of platelet activation and potential therapeutic effects of natural drugs

BACKGROUND

Cardiovascular disease is one of the most concerning chronic diseases in the world. Many studies have shown that platelet overactivation is a very important factor in the occurrence and development of cardiovascular diseases. At present, the widely used antiplatelet drugs have some defects, such as drug resistance and adverse reactions.

PURPOSE

The purpose of this article is to summarize the main mechanisms and pathways of platelet activation, the main targets of antiplatelet aggregation, and the antiplatelet aggregation components of natural drugs and their mechanisms of action to provide new research ideas for the development and application of antiplatelet drugs.

STUDY DESIGN AND METHODS

In this review, we systematically searched the PubMed, Google Scholar, Web of Science, and CNKI databases and selected studies based on predefined eligibility criteria. We then assessed their quality and extracted data.

RESULTS

ADP, AA, THR, AF, collagen, SDF-1α, and Ca²⁺ can induce platelet aggregation and trigger thrombosis. Natural drugs have a good inhibitory effect on platelet activation. More than 50 kinds of natural drugs and over 120 kinds of chemical compounds, including flavonoids, alkaloids, saponins, terpenoids, coumarins, and organic acids, have significantly inhibited platelet activation activity. The MAPK pathway, cGMP-PKG pathway, cAMP-PKA pathway, PI3K-AKT pathway, PTK pathway, PLC pathway, and AA pathway are the main mechanisms and pathways of platelet activation.

CONCLUSION

Natural drugs and their active ingredients have shown good activity and application prospects in anti-platelet aggregation. We hope that this review provides new research ideas for the development and application of antiplatelet drugs.

The Leaf Extract of Mitrephora chulabhorniana Suppresses Migration and Invasion and Induces Human Cervical Cancer Cell Apoptosis through Caspase-Dependent Pathway

Cervical cancer is rated to be the leading cause of cancer-related death in women worldwide. Since screening test and conventional treatments are less accessible for people in developing countries, an alternative use of medicinal plants exhibiting strong anticancer activities may be an affordable means to treat cervical cancer. Mitrephora chulabhorniana (MC) is the newly identified species; however, its biological functions including anticancer activities have been largely unexplored. Hence, in this study, we were interested in investigating anticancer effects of this plant on the human cervical cell line (HeLa). MC extract was profiled for phytochemicals by TLC. This plant was tested to contain alkaloids, flavonoids, and terpenes. HeLa cells were treated with MC extract to investigate the anticancer activities. Cytotoxicity and viability of cells treated with MC were determined by MTT assay and Trypan blue exclusion assay. Cell migration was tested by wound healing assay, and cell invasion was determined by Transwell assay. The level of caspase 7, caspase 9, and PARP was determined by western blot analysis. We found that the leaf extract of MC strongly reduced cancer cell survival rate. This finding was consistent with the discovery that the extract dramatically induced apoptosis of cervical cancer cells through the activation of caspase 7 and caspase 9 which consequently degraded PARP protein. Furthermore, MC extract at lower concentrations which were not cytotoxic to the cancer cells showed potent inhibitory activities against HeLa cervical cancer cell migration and invasion. Mitrephora chulabhorniana possesses its pharmacological properties in inhibiting cervical cancer cell migration/invasion and inducing apoptotic signaling. This accumulated information suggests that Mitrephora chulabhorniana may be a beneficial source of potential agents for cervical cancer treatment.

Toxicity and mode of action of the aporphine plant alkaloid liriodenine on the insect GABA receptor

Liriodenine is a biologically active plant alkaloid with multiple effects on mammals, fungi, and bacteria, but has never been evaluated for insecticidal activity. Accordingly, liriodenine was applied topically in ethanolic solutions to adult female Anopheles gambiae, and found to be mildly toxic. Its lethality was synergized in mixtures with dimethyl sulfoxide and piperonyl butoxide. Recordings from the ventral nerve cord of larval Drosophila melanogaster showed that liriodenine was neuroexcitatory and reversed the inhibitory effect of 1 mM GABA at effective concentrations of 20-30 μM. GABA antagonism on the larval nervous system was equally expressed on both susceptible and cyclodiene-resistant rdl preparations. Acutely isolated neurons from Periplaneta americana were studied under patch clamp and inhibition of GABA-induced currents with an IC₅₀ value of about 1 μM were observed. In contrast, bicuculline did not reverse the effects of GABA on cockroach neurons, as expected. In silico molecular models suggested reasonable structural concordance of liriodenine and bicuculline and isosteric hydrogen bond acceptor sites. This study is the first assessing of the toxicology of liriodenine on insects and implicates the GABA receptor as one likely neuronal target, where liriodenine might be considered an active chemical analog of bicuculline.

Luteolin and apigenin derived glycosides from Alphonsea elliptica abrogate LPS-induced inflammatory responses in human plasma

ETHNOPHARMACOLOGICAL RELEVANCE

Numerous Alphonsea species including Alphonsea elliptica (mempisang) leaves and fruits are indigenously used in inflammatory conditions such as postpartum swelling and rheumatism in southeast Asian countries. In our previous in-vitro findings, A. elliptica methanol extract exhibited platelet-activating factor inhibition, suggesting the presence of phyto-constituents with anti-inflammatory potential.

AIM OF THE STUDY

However, so far there is no literature available on the anti-inflammatory activity of this species. Henceforth, based on the above background and our previous laboratory findings, we hypothesize that phytoconstituents of A. elliptica could possess anti-inflammatory potential against inflammatory mediators including prostaglandin-E₂ (PGE₂), cyclooxegenase-2 (COX-2) and cytokines (IL-1β and IL-6).

MATERIALS AND METHODS

Vacuum and column chromatography techniques were employed for the isolation of phytoconstituents. The structure elucidation was carried out using HRESI-MS, ¹H and ¹³C-NMR analysis and compared with the published literature. For cytotoxicity analysis, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed on peripheral blood mononuclear cells. In-vitro anti-inflammatory activities were evaluated against the levels of PGE₂, COX-2, IL-1β and IL-6 in lipopolysaccharide (LPS)-induced human plasma using enzyme-linked immunosorbent assay and radioimmunoassay.

RESULTS

Unprecedentedly, chromatographic purification of methanolic leaves extract afforded five flavones namely vitexin, isovitexin, orientin, isoorientin, schaftoside with three flavanols; kaempferol, myricetin and rutin from A elliptica. In cell viability analysis, isolates did not present cytotoxicity up to 50 μM. In anti-inflammatory evaluation, orientin and isoorientin exhibited strong (≥70%), while isovitexin and vitexin produced strong to moderate (50-69%) PGE₂, COX-2, IL-1β and IL-6 inhibition at 25 and 50 μM. Isoorientin, orientin, isovitexin, and vitexin showed significant (p < 0.05) and concentration-dependent PGE₂ inhibition with IC₅₀ values (μM) of 11.40, 14.71, 17.70 and 20.58 against indomethacin (8.80). Furthermore, isoorientin, orientin, isovitexin, and vitexin produced significant concentration-dependent inhibition with IC₅₀ values (μM) of COX-2: 7.13, 9.51, 12.81, 16.61; IL-1β 4.80, 6.20, 10.85, 14.51; IL-6: 4.01, 5.90, 11.51 and 14.88 as compared to dexamethasone: 5.29, 2.93, 3.72, respectively (p < 0.05).

CONCLUSION

Conclusively, isolated phytoconstituents are reported for the first time from the A. elliptica. Moreover, isovitexin, vitexin orientin and isoorientin abrogated LPS-induced inflammatory responses in human plasma at non-cytotoxic concentrations.

A new prenylated benzoquinone from Cyathocalyx pruniferus abrogates LPS-induced inflammatory responses associated with PGE2, COX-2 and cytokines biosynthesis in human plasma

In our previous laboratory findings, Cyathocalyx pruniferus extracts exhibited platelet-activating factor inhibition, suggesting their anti-inflammatory potential. Hence, this study was designed with the aim to isolate phyto-constituents from C. pruniferus with potent anti-inflammatory activities. Column and volume liquid chromatography were used for isolation of phyto-constituents. The structure elucidation was carried out using spectroscopic analysis (HRESI-MS, ¹H and ¹³C-NMR) and compared with published literature. For cytotoxicity analysis, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide assay was performed on peripheral blood mononuclear cells. Anti-inflammatory activities were evaluated against the levels of inflammatory cytokines (IL-1β and IL-6), prostaglandin-E₂ (PGE₂) and cyclooxegenase-2 (COX-2), in lipopolysaccharide (LPS)-induced human plasma using ELISA and radioimmunoassay (RIA). The chromatographic purification of methanol leaves extract afforded 13 (1-13) secondary metabolites. Additionally, cytotoxicity analysis suggested that isolates were non-cytotoxic at 100 μM. In anti-inflammatory evaluation, 2-octaprenyl-1, 4-benzoquinone (5) produced strong (≥ 70%) inhibition of PGE₂, COX-2, IL-1β and IL-6 at 50 µM. Moreover, 2-octaprenyl-1,4-benzoquinone (5) exhibited concentration-dependent inhibition with IC₅₀ values (µM) of 11.21, 6.61, 2.20 and 3.56 as compared to controls; indomethacin for PGE₂ (11.84) and dexamethasone in COX-2 (5.19), IL-1β (1.83) and IL-6 (3.76) analysis, respectively. In conclusion, two new compounds including 2-octaprenyl-1, 4-benzoquinone (5) and 14-methyloctadec-1-ene (6) are reported for the first time from plant species. Additionally, 2-octaprenyl-1, 4-benzoquinone (5) dose-dependently suppressed the production of pro-inflammatory mediators involved in acute and chronic inflammation at non-cytotoxic concentrations.

Cytotoxic compounds from the leaves and stems of the endemic Thai plant Mitrephora sirikitiae

Context: Mitrephora sirikitiae Weeras., Chalermglin & R.M.K. Saunders (Annonaceae) is a plant endemic to Thailand. Its constituents and their biological activities are unknown.Objective: Isolation and identification of the compounds in the leaves and stems of M. sirikitiae and determination of their cytotoxicity.Materials and methods: Methanol extracts of the leaves and stems of M. sirikitiae were separated by chromatography, and spectroscopic methods were used to determine the structures of the components. The cytotoxicity of the extracts and pure compounds was evaluated using the sulforhodamine B assay with several cell lines. The cells were treated with the compounds at concentrations of 0.16-20 µg/mL for 48 or 72 h.Results: The investigation of the extracts of M. sirikitiae leaves and stems resulted in the isolation of a new lignan, mitrephoran, and 15 known compounds. Among these compounds, 2-(3,4-dimethoxyphenyl)-6-(3,5-dimethoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane, ciliaric acid, 6-methoxymarcanine A, and stepharanine were isolated from this genus for the first time. The alkaloids liriodenine and oxoputerine exhibited strong cytotoxicity against all tested cells (IC₅₀ values of 6.59-11.02 µM). In contrast, magnone A, 3',4-O-dimethylcedrusin, and 6-methoxymarcanine A inhibited the growth of some of the tested cells (IC₅₀ values of 2.03-19.73 µM). Magnone A and 6-methoxymarcanine A showed low toxicity for Hek 293 cells (IC₅₀ >20 µM).Discussion and conclusions: M. sirikitiae is a source of cytotoxic lignans and alkaloids. Among the cytotoxic compounds, magnone A and 6-methoxymarcanine A are potentially useful lead compounds for the further development of anticancer agents because of their selective inhibitory effects on cancer cell lines.

In vivo and in vitro evaluation of hair growth potential of Cacumen Platycladi, and GC-MS analysis of the active constituents of volatile oil

ETHNOPHARMACOLOGICAL RELEVANCE

Cacumen Platycladi (CP) is the leaves of Platycladus orientalis which has been traditionally used to resist alopecia and promote hair growth. However, no study has been reported on the effects of CP on proliferation of dermal papilla cells (DPCs). And there is also no complete and systematic research on hair re-growth efficacies of CP.

AIM OF THE STUDY

To evaluate the hair-growth activity of their extracts on the proliferation of DPCs and the promotion of hair reproduction in C57BL/6 mice.

MATERIALS AND METHODS

For the DPCs, different extract fractions of CP were investigated. The hair growth effect of CP volatile oil on C57BL/6 mice was evaluated for 28 days. Meanwhile, the chemical constituents of the volatile oil from Cacumen Platycladi were isolated and identified by GC-MS.

RESULTS

The study showed that the extracts of CP could promote the proliferation of DPCs, and the activity of volatile oil was the best. CP volatile oil (100 μg/mL) resulted in stronger proliferation of DPCs by 239.8% compared with control (100%) and minoxidil (130.3%) during the 48 h incubation. And no obvious cytotoxic activity was observed when volatile oil was dosed up to 500 μg/mL. At different growth stages, mice treated with 0.2 g/kg CP volatile oil required shorter time than 2% minoxidil. Hair length for 0.2 g/kg CP volatile oil treated group was longer than those of minoxidil and control. Further histological observation indicated that CP volatile oil could prolonged the anagen phase of hair follicles. Moreover, thirty four components, with contents of 81.9% of the total volatile oils, were separaed and identified.

CONCLUSION

The CP volatile oil may have the potential therapeutic agent for the treatment of alopecia.

Hair growth promotion effect of cedrol cream and its dermatopharmacokinetics

Topical use of cedrol ethanol has been reported to have a beneficial effect on hair loss. However, the use of cedrol has been limited by application-related issues, such as poor water solubility and volatile features. Therefore, the present study developed a cream formulation of cedrol and evaluated various physicochemical parameters of the prepared cream. The optimized cedrol cream was selected after orthogonal tests and determined further. The dermatopharmacokinetics were studied to investigate the absorption difference between cedrol cream and cedrol ethanol after dermal application, and the concentrations of cedrol in skin were analysed by the gas chromatography-mass spectrometry (GC-MS) method. By comparison, the area under the curve (AUC_{0–24 h}) of cedrol cream was almost three times higher than that of cedrol ethanol. Moreover, this study was undertaken to evaluate the hair growth promoting efficacy of cedrol cream in C57BL/6 mice and Wistar rats. Macroscopic assessment and alopecia score showed that C57BL/6 mice treated with cedrol cream showed a faster production of pigmentation and a higher score at different growth stages than other groups. The hair length of the cedrol cream-treated group was much longer than those of the cedrol ethanol and minoxidil groups. Histological analyses indicated that in the cedrol ethanol group, most follicles of the C57BL/6 mice were in the catagen phase, whereas nearly 83% of hair follicles in the cedrol cream group remained in the anagen phase. Taken together, our data strongly suggest that the cream formulation of cedrol has a stronger hair growth promotion effect, gave no irritation and was safe for topical administration.

Topical use of cedrol ethanol has been reported to have a beneficial effect on hair loss.

Annonaceae: Breaking the Wall of Inflammation

Inventories of tropical forests have listed Annonaceae as one of the most diverse plant families. For centuries, it is employed in traditional medicines to cure various pathological conditions including snakebite, analgesic, astringent, diarrhea, dysentery, arthritis pain, rheumatism, neuralgia, and weight loss etc. Phytochemical analysis of Annonaceae family have reported the occurrence of alkaloids, flavonoids, triterpenes, diterpenes and diterpene flavone glycosides, sterols, lignans, and annonaceous acetogenin characteristically affiliated with Annonaceae sp. Numerous past studies have underlined the pleotropic pharmacological activities of the crude extracts and isolated compounds from Annonaceae species. This review is an effort to abridge the ethnobotany, morphology, phytochemistry, toxicity, and particularly focusing on the anti-inflammatory activity of the Annonaceae species.

Association of platelet-activating factor receptor gene rs5938 (G/T) and rs313152 (T/C) polymorphisms with coronary heart disease and blood stasis syndrome in a Chinese Han population

OBJECTIVE

To explore the association of the platelet-activating factor receptor (PAFR) gene rs5938, rs313152 and rs76744145 polymorphisms with coronary heart disease (CHD) and blood stasis syndrome (BSS) of CHD in Chinese Han population.

METHODS

A total of 570 CHD patients (299 with BSS and 271 with non-BSS) and 317 controls were enrolled. The PAFR gene rs5938, rs313152 and rs76744145 polymorphisms were genotyped using the multiplex SNaPshot technology. The statistical analysis was conducted using a multiple variable logistic regression model.

RESULTS

Significant differences were detected in the genotypes frequency distributions of the rs5938 (P<0.01), but not the rs313152 (P>0.05), between the controls and CHD patients. Individuals with an rs5938 or rs313152 mutated allele had a low risk for CHD [adjusted odds ratio (aOR)=0.35, 95% confidence interval (CI): 0.23 to 0.56, P<0.01; aOR=0.65, 95% CI: 0.46 to 0.91, P<0.05, respectively]. After the CHD patients were stratified as BSS or non-BSS according to their Chinese medicine patterns, the rs5938 polymorphism mutated alleles had a significant association with a low risk for BSS of CHD (aOR=0.32, 95% CI: 0.18 to 0.57, P<0.01) and non-BSS of CHD (aOR=0.31, 95% CI: 0.17 to 0.55, P<0.01). The rs313152 polymorphism was associated with a low risk for BSS (aOR=0.51, 95% CI: 0.33 to 0.79, P<0.01), but not for non-BSS (aOR=1.22, 95% CI: 0.81 to 1.85, P<0.05). Furthermore, the interaction effect of the rs5938 and rs313152 polymorphisms for BSS of CHD was significantly based on an aOR value associated with the combination of the rs5938 GT genotype with the rs313152 TC genotype of 0.27 (95% CI: 0.1 to 0.7, P<0.01).

CONCLUSION

The PAFR gene rs5938 or rs313152 polymorphisms might be a potential biomarker for susceptibility to CHD, especially to BSS of CHD in Chinese Han population.

Quebrachitol: Global Status and Basic Research

Recently, there has been a renewed interest in the natural-products-inspired drugs. Quebrachitol (QCT) is one of naturally occurring optically active cyclitols that has now received considerable attention. Until the last decade, it came to be a starting point for the lead discovery. In this review, we had a discussion on the basic research of QCT, including its source, structure, properties, and the recent advances on its application. The biological activities and QCT-inspired leads that are potentially effective for treating human diseases were also discussed.

Preventive effects of cedrol against alopecia in cyclophosphamide-treated mice

Although numerous hypotheses have been proposed to prevent chemotherapy-induced alopecia (CIA), effective pharmaceuticals have yet to be developed. In our study, the back hairs of C57BL/6 mice were factitiously removed. These mice were then treated with cedrol or minoxidil daily. Mice with early-stage anagen VI hair follicles were treated with cyclophosphamide (CYP, 125mg/kg) to induce alopecia. The CYP-damaged hair follicles were observed and quantified by using a digital photomicrograph. The results demonstrated that the minoxidil-treated mice suffered from complete alopecia similar to the model 6days after CYP administration. Simultaneously, the cedrol-treated (200mg/kg) mice manifested mild alopecia with 40% suppression. Histological observation revealed that anagen hair follicles of the cedrol-pretreated mice (82.5%) likely provided from damage compared with the sparse and dystrophic hair follicles of the model mice (37.0%). Therefore, the use of topical cedrol can prevent hair follicle dystrophy and provide local protection against CIA.

Methyl-inositol, γ-aminobutyric acid and other health benefit compounds in the aril of litchi

The available components in the flesh of litchi seem insufficient to interpret its wide and significant physiological effects. Some unusual compounds, including myo-inositol, inositol methyl derivatives and γ-aminobutyric acid (GABA) were identified as main constituents in the flesh of litchi. Their concentrations varied among cultivars but remain relatively constant during development. Litchi flesh was shown to contain moderate myo-inositol (0.28-0.78 mg g(-1) FW), ascorbic acid (0.08-0.39 mg g(-1) FW) and phenolics (0.47-1.60 mg g(-1) FW), but abundant l-quebrachitol (1.6-6.4 mg g(-1) FW) and GABA (1.7-3.5 mg g(-1) FW). The concentration of GABA in the flesh of litchi was about 100 times higher than in other fruits. And l-quebrachitol is not a common component in fruits. The biological and physiological activities of inositols, inositol derivatives and GABA have been extensively documented. These compounds are probably important compositional characteristic contributing to the widely shown health benefits of litchi.

The "Other" Inositols and Their Phosphates: Synthesis, Biology, and Medicine (with Recent Advances in myo-Inositol Chemistry)

Cell signaling via inositol phosphates, in particular via the second messenger myo-inositol 1,4,5-trisphosphate, and phosphoinositides comprises a huge field of biology. Of the nine 1,2,3,4,5,6-cyclohexanehexol isomers, myo-inositol is pre-eminent, with "other" inositols (cis-, epi-, allo-, muco-, neo-, L-chiro-, D-chiro-, and scyllo-) and derivatives rarer or thought not to exist in nature. However, neo- and d-chiro-inositol hexakisphosphates were recently revealed in both terrestrial and aquatic ecosystems, thus highlighting the paucity of knowledge of the origins and potential biological functions of such stereoisomers, a prevalent group of environmental organic phosphates, and their parent inositols. Some "other" inositols are medically relevant, for example, scyllo-inositol (neurodegenerative diseases) and d-chiro-inositol (diabetes). It is timely to consider exploration of the roles and applications of the "other" isomers and their derivatives, likely by exploiting techniques now well developed for the myo series.

Plant extracts inhibit ADP-induced platelet activation in humans: their potential therapeutic role as ADP antagonists

Adenosine diphosphate (ADP) plays a pivotal role in platelet activation. Platelet hyperactivity is associated with vascular disease and also has a key role in haemostasis and thrombosis. ADP activates platelets through three purinoceptor subtypes, the G(q)-coupled P2Y(1) receptor, G(i)-coupled P2Y(12) receptor and P2X(1) ligand-gated cation channel. Platelet ADP purinergic receptors are therefore suitable targets for antiplatelet drugs. Thienopyridines such as clopidogrel and ticlopidine, as well as other ADP receptor antagonists like prasugrel, ticagrelor, cangrelor and elinogrel have demonstrated clinical benefits via the inhibition of the selective purinergic ADP receptor, P2Y(12). However, they still have limitations in their mode of action and efficacy, like increased risk of bleeding. Thus, the ongoing pursuit to develop newer and more effective antiplatelet agents continues. There is a growing interest in the purinergic antiplatelet properties exhibited by plant extracts. This article considers the following: pomolic acid isolated from Licania pittieri, brazilin isolated from the heartwood of Caesalpinia sappan L, phylligenin isolated from the twigs of Muraltia vulpina, bark oil of Gonystylus velutinus, seed and bark extracts from Aesculus hippocastanum L. and red wine phenolics and catechins isolated from green tea. Moreover, the method used to investigate platelet purinergic receptors should be considered, since using a more sensitive, high-resolution platelet sizer can sometimes detect platelet variations when the light transmission method was not able to do so. The exact mechanisms by which these plant extracts work need further investigation. They all however inhibit ADP-induced activation in human platelets. This could explain, at least in part, the protective effect of plant extracts as antiplatelet agents.

Ent-pimarane and ent-trachylobane diterpenoids from Mitrephora alba and their cytotoxicity against three human cancer cell lines

Bioassay-guided fractionation of the hexane extract of the branches of Mitrephora alba led to the isolation of five diterpenoids: ent-8β-hydroxypimar-15-en-18-oic acid, ent-15,16-dihydroxypimar-8(14)-en-18-oic acid, ent-3β-hydroxytrachyloban-18-oic acid, ent-3β-hydroxytrachyloban-18-al and methyl ent-3β-hydroxytrachyloban-18-oate, together with five related known diterpenoids. The structures were elucidated by spectroscopic analysis and comparison with literature data. All isolated compounds were evaluated for their cytotoxic activities against three human cancer cell lines. The results showed that three ent-trachylobane diterpenes had moderate cytotoxicity against NCI-H187 cancer cells.

Platelet-activating factor (PAF)-antagonists of natural origin

Presently herbal medicines are being used by about 80% of the world population for primary health care as they stood the test of time for their safety, efficacy, cultural acceptability and lesser side effects. The discovery of platelet activating factor antagonists (PAF antagonists) during these decades are going on with different framework, but the researchers led their efficiency in studying in vitro test models. Since it is assumed that PAF play a central role in etiology of many diseases in humans such as asthma, neuronal damage, migraine, cardiac diseases, inflammatory, headache etc. Present days instinctively occurring PAF antagonist exists as a specific grade of therapeutic agents for the humans against these and different diseases either laid hold of immunological or non-immunological types. Ginkgolide, cedrol and many other natural PAF antagonists such as andrographolide, α-bulnesene, cinchonine, piperine, kadsurenone, different Piper species' natural products and marine origin plants extracts or even crude drugs having PAF antagonist properties are being used currently against different inflammatory pathologies. This review is an attempt to summarize the data on PAF and action of natural PAF antagonists on it, which were evaluated by in vivo and in vitro assays.

Platelet-activating factor (PAF) antagonistic activity of a new biflavonoid from Garcinia nervosa var. pubescens King

The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using ³H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC₅₀ values of 28.0 and 20.4 µM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant.

Inhibitory effects of acetylmelodorinol, chrysin and polycarpol from Mitrella kentii on prostaglandin E₂ and Thromboxane B₂ production and platelet activating factor receptor binding

Acetylmelodorinol, chrysin and polycarpol, together with benzoic acid, benzoquinone and stigmasterol were isolated from the leaves of Mitrella kentii (Bl.) Miq. The compounds were evaluated for their ability to inhibit prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) production in human whole blood using a radioimmunoassay technique. Their inhibitory effect on platelet activating factor (PAF) receptor binding to rabbit platelet was determined using ³H-PAF as a ligand. Among the compounds tested, chrysin showed a strong dose-dependent inhibitory activity on PGE₂ production (IC₅₀ value of 25.5 µM), which might be due to direct inhibition of cyclooxygenase-2 (COX-2) enzymatic activity. Polycarpol, acetylmelodorinol and stigmasterol exhibited significant and concentration-dependent inhibitory effects on TXB₂ production with IC₅₀ values of 15.6, 19.1 and 19.4 µM, respectively, suggesting that they strongly inhibited COX-1 activity. Polycarpol and acetylmelodorinol showed strong dose-dependent inhibitory effects on PAF receptor binding with IC₅₀ values of 24.3 and 24.5 µM, respectively.