Pharmacological insights into the multifaceted biological properties of quinic acid

Quinic acid is a cyclohexanecarboxylic acid contained in the extracts of several parts of medicinal plants including Haematocarpus validus, Hypericum empetrifolium, Achillea pseudoaleppica, Rumex nepalensis, Phagnalon saxatile subsp. saxatile, Coffea arabica, Ziziphus lotus L, and Artemisia annua L … etc. Currently, in vitro and in vivo pharmacological studies showed that quinic acid exhibits various biological activities, such as antioxidant, antidiabetic, anticancer activity, antimicrobial, antiviral, aging, protective, anti-nociceptive and analgesic effects. Indeed, QA possesses an important antibacterial effect which could be explained by the fact that this molecule modules the functions of ribosomes and the synthesis of aminoacyl-tRNAs, modifications the levels of glycerophospholipids and fatty acids and disruption of the oxidative phosphorylation pathway thereby causing interference with membrane fluidity. The antidiabetic activity of AQ is achieved by stimulation of insulin secretion via the mobilization of Ca2+ from intracellular reserves and the increase in the NAD(P)H/NAD(P)+ ratio. Its anticancer effect is through the promotion of apoptosis, inhibition of activator protein 1 (AP-1) and signaling pathways involving protein kinase C (PKC) and certain mitogen-activated protein kinases (MAPKs), resulting in the downregulation of matrix metallopeptidase 9 (MMP-9) expression. Therefore, this review describes the main research work carried out on the biological properties of AQ and the mechanism of action underlying some of these effects, as well as the investigations of the main pharmacokinetic studies.

Polyphenols of the Inuleae-Inulinae and Their Biological Activities: A Review

Polyphenols are ubiquitous plant metabolites that demonstrate biological activities essential to plant-environment interactions. They are of interest to plant food consumers, as well as to the food, pharmaceutical and cosmetic industry. The class of the plant metabolites comprises both widespread (chlorogenic acids, luteolin, quercetin) and unique compounds of diverse chemical structures but of the common biosynthetic origin. Polyphenols next to sesquiterpenoids are regarded as the major class of the Inuleae-Inulinae metabolites responsible for the pharmacological activity of medicinal plants from the subtribe (Blumea spp., Dittrichia spp., Inula spp., Pulicaria spp. and others). Recent decades have brought a rapid development of molecular and analytical techniques which resulted in better understanding of the taxonomic relationships within the Inuleae tribe and in a plethora of data concerning the chemical constituents of the Inuleae-Inulinae. The current taxonomical classification has introduced changes in the well-established botanical names and rearranged the genera based on molecular plant genetic studies. The newly created chemical data together with the earlier phytochemical studies may provide some complementary information on biochemical relationships within the subtribe. Moreover, they may at least partly explain pharmacological activities of the plant preparations traditionally used in therapy. The current review aimed to systematize the knowledge on the polyphenols of the Inulae-Inulinae.

New caffeoyl derivatives with potent DPPH radical scavenging activity from Elephantopus tomentosus

Eight new caffeoyl derivatives, elephantomentosides A-H (1 - 8), together with ten known ones (9 - 18), were isolated from the whole plant of Elephantopos tomentosus L. Their structures were elucidated using detailed spectroscopic analysis. Structurally, compounds 1 - 8 are composed of β-D-glucopyranose, and almost all of the substituent positions are at the C-1' and C-4' of glucopyranose. The anti-inflammatory and antioxidant activities of all isolated compounds were evaluated in vitro. Compounds 9-10, 13-15, and 17-18 exhibited significant DPPH scavenging capacity with IC50 values in the range of 10.01-25.07 μM, in comparison with Vc (IC50, 17.98 μM).

Acyl-quinic acids from the root bark of Acanthopanax gracilistylus and their inhibitory effects on neutrophil elastase and cyclooxygenase-2 in vitro

Eleven new acyl-quinic acids (AQAs) 1a-9, and 18 known AQAs 10-27 were isolated from the root bark of Acanthopanax gracilistylus W. W. Smith (Acanthopanacis Cortex). The planar structures of 1a-9 were determined based on their HR-ESIMS, IR, and NMR data. The absolute configurations of 1a-6 were identified by comparing the experimental and the calculated electronic circular dichroism (ECD) spectra. This is the first report of the isolation of AQAs from Acanthopanacis Cortex. Notably, 1a-6 were determined as unusual oxyneolignan-(-)-quinic acids heterodimers, representing a new class of natural products. The inhibitory activities of 1a-27 on neutrophil elastase (NE) and cyclooxygenase-2 (COX-2) were studied in vitro, and the results indicated they possessed significant inhibitory activities on COX-2. Among them, the IC50 values of 1a-9 were 0.63±0.014, 0.75±0.028, 0.15±0.023, 0.63±0.016, 0.30±0.013, 35.63±4.600, 8.70±1.241, 16.51±0.480, 0.69±0.049, 0.39±0.017, and 0.26±0.080 μM, respectively. This study represents the inaugural disclosure of the anti-COX-2 constituents found in Acanthopanacis Cortex, thereby furnishing valuable insights into the exploration of novel COX-2 inhibitors derived from natural reservoirs.

Galium aparine L. protects against acetaminophen-induced hepatotoxicity in rats

The toxicity of acetaminophen (N-acetyl-para-aminophenol (APAP)) is the most frequent cause of drug-induced liver damage. Galium aparine L. (GA) is traditionally used to treat jaundice. We aimed to investigate the hepatoprotective potential of GA in the APAP-induced hepatic encephalopathy (HE) rat model. Qualitative phytochemical characterization of GA was performed by LC/Q-TOF/MS analysis. Wistar rats were pretreated with GA (250 and 500 mg/kg b.wt. per oral) for five days. On the 6th day, the rats were exposed to APAP (1500 mg/kg b.wt. oral gavage) and behavioral tests (open field and passive avoidance tests) were applied on the 7th and 8th days. The animals were killed, and biochemical and histopathological parameters were assessed in blood and hepatic specimens. GA pretreated rats exhibited a significant reduction in APAP-induced liver damage, evidenced by the reduction in liver necrosis and alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin (BIL). GA demonstrated an anxiolytic effect, as seen in the acquisition trial and grooming behavior. The short-term memory performances of animals were not changed in all groups, suggesting that APAP intoxication did not affect hippocampal function. These results show that GA extract markedly exerts hepatoprotective activity, while its effect on hepatic encephalopathy was limited.

The chemical composition of the flowers essential oil of Inula crithmoides (Asteraceae) growing in aeolian islands, Sicily (Italy) and its biocide properties on microorganisms affecting historical art crafts

Essential oils have been used for a long time in several fields of interest. Recently, they have also been applied in the conservation of Cultural Heritage to contrast biodeterioration replacing the most current biocides toxic for humans and environment. Inula crithmoides L. (syn. Limbarda crithmoides (L.) Dumort) is a halophyte species distributed along the Mediterranean coasts and it is used as an edible vegetable since the young leaves or shoots are eaten raw or cooked. Several biological properties have been determined for this plant including antimicrobial activities. In this study the volatile composition of the aerial part of an accession from the Aeolian Islands, Sicily (Italy) is described. Furthermore, the in vitro antibacterial assay against four species of bacteria isolated from a XX century Tholu Bhommalu, a leather painted puppet from Andhra Pradesh (India), was showed by the Agar disc diffusion method.

Medicinal Inula Species: Phytochemistry, Biosynthesis, and Bioactivities

As a genus of the Asteraceae, Inula is widely distributed all over the world, and several of them are being used in traditional medicines. A number of metabolites were isolated from Inula species, and some of these have shown to possess ranges of pharmacological activities. The genus Inula contains abundant sesquiterpenoids, such as eudesmanes, xanthanes, and sesquiterpenoid dimers and trimers. In addition, other types of terpenoids, flavonoids, and lignins also exist in the genus Inula. Since 2010, more than 300 new secondary metabolites, including several known natural products that were isolated for the first time from the genus Inula. Most of them exhibited potential bioactivities in various diseases. The review aimed to summarize the advance of recent researches (2010-2020) on phytochemical constituents, biosynthesis, and pharmacological properties of the genus Inula for providing a scientific basis and supporting its application and exploitation for new drug development.

Current Advances in Naturally Occurring Caffeoylquinic Acids: Structure, Bioactivity, and Synthesis

Caffeoylquinic acids (CQAs) are a broad class of secondary metabolites that have been found in edible and medicinal plants from various families. It has been 100 years since the discovery of chlorogenic acid in 1920. In recent years, a number of naturally derived CQAs have been isolated and structurally elucidated. Accumulated evidence demonstrate that CQAs have a wide range of biological activities, such as antioxidation, antibacterial, antiparasitic, neuroprotective, anti-inflammatory, anticancer, antiviral, and antidiabetic effects. Up to date, some meaningful progresses on the biosynthesis and total synthesis of CQAs have also been made. Therefore, it is necessary to comprehensively summarize the structure, biological activity, biosynthesis, and chemical synthesis of CQAs. This review provides extensive coverage of naturally occurring CQAs discovered from 1990 until 2020. Modern isolation techniques, chemical data (including structure, biosynthesis, and total synthesis), and bioactivity are summarized. This would be helpful for further research of CQAs as potential pharmaceutical agents.

Isolation, structure elucidation and neuroprotective effects of caffeoylquinic acid derivatives from the roots of Arctium lappa L

Five undescribed caffeoylquinic acid derivatives (CQAs), along with fifteen known CQAs, were isolated from the roots of Arctium lappa L.(burdock). The chemical structures of compounds were determined using extensive spectroscopic analyses, including UV, IR, NMR and MS. Further in vitro bioactive investigation demonstrated the neuroprotective effects of these compounds against the neurotoxicity of hydrogen peroxide (H₂O₂) and N-methyl-D-aspartate (NMDA). 1,3,5-tri-O-caffeoylquinic acid and 1,4,5-tri-O-caffeoylquinic acid significantly reduced H₂O₂-induced human neuroblastoma SH-SY5Y cell death with concentration for 50% of maximal effect (EC₅₀) values of 17.3 and 19.3 μM. Meanwhile, 3,5-di-O-caffeoyl-1-O-maloylquinic acid displayed protective effect against NMDA-induced cell injury with EC₅₀ values of 18.4 μM. Overall, the more caffeoyl, the better the antioxidant activity, while the maloyl-containing compounds had better anti-NMDA activity.

Bioassay-Guided Isolation of Antiproliferative Compounds from Limbarda crithmoides (L.) Dumort

Limbarda crithmoides (L.) Dumort (Asteraceae) n-hexane extract displayed high cell proliferation inhibitory activity against acute myeloid leukaemia cells (OCI-AML3) and was therefore subjected to a bioassay-guided multistep separation procedure. Two thymol derivatives, namely 10-acetoxy-8,9-epoxythymol tiglate (1) and 10-acetoxy-9-chloro-8,9-dehydrothymol (2), were isolated and identified by means of NMR spectroscopy. Both of them exhibited a significant dose-dependent inhibition of cell proliferation.

Intestinal α-Glucosidase Inhibitors in Achillea millefolium

Achillea millefolium is a plant used as a component of anti-diabetic preparation but the bioactive compounds responsible for its use are not known. Inhibition of intestinal α-glucosidase is a preferable effect for prevention and treatment of diabetes, and A. millefolium extract showed inhibitory activity against the enzyme. Activity-guided separation of the extract gave four mono- or di-caffeoylquinic acids as the isolate. Quantitation of these four caffeoylquinic acids and the activity of the isolates suggested that these are the major contributor for the α-glucosidase inhibitory activity in the extract. However also, the presence of unidentified, minor, but potent α-glucosidase inhibitor in the isolate was also suggested.

Cornigerin, a new sesqui-lignan from the hepatoprotective fractions of Cynara cornigera L

The ethanol extract of Cynara cornigera L. was fractionated and the fractions were subjected to hepatoprotective assays using Wistar albino rats at a dose of 500 and 250mg/kg. The liver injury was induced in rats using carbon tetrachloride. Biochemical parameters such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and total bilirubin were estimated as reflections of the liver condition, with silymarin as a positive control. Phytochemical investigation and chromatographic separation of the hepatoprotective fractions led to the isolation of a new sesqui-lignan namely cornigerin (1), along with eight known compounds: apigenin (2), luteolin (3), β-sitosterol glycoside (4), apigenin 7-O-β-D-glucopyranoside (5), luteolin-7-O-β-D-glucopyranoside (6), apigenin-7-O-rutinoside (7), cynarin 1,5-di-O-caffeoylquinic acid (8), and apigenin-7-O-β-D-glucuronide (9). This is the first report for the isolation of 8 and 9 from this plant.

Metabolomic Profile of the Genus Inula

Plants have a long history as therapeutics in the treatment of human diseases and have been used as source of medicines for ages. Searching for new biologically active natural products, many plants and herbs are screened for natural products with pharmacological activities. In this field, the genus Inula, which comprises more than 100 species, several of them being used in traditional medicine, is very important, especially due to the finding that several of the isolated pure secondary metabolites proved to possess important biological activities. Inula species have been reported as rich sources of sesquiterpene lactones, including eudesmanes, germacranes, guaianes, and dimeric structures, and since 2006 ca. 400 secondary metabolites, including more than 100 new natural products, some of them with relevant pharmacological activities, have been identified. Herein, we critically compile and update the information regarding the types of secondary metabolites found in the genus Inula and the progress in their isolation.

Anti-Inflammatory Constituents from Bidens frondosa

A new polyacetylene glucoside (3E,5E,11E)-tridecatriene-7,9-diyne-1,2,13-triol-2-O-β-D-glucopyranoside (1), a new phenylpropanoid glucoside 2'-butoxyethylconiferin (2), and a new flavonoid glycoside 8,3',4'-trihydroxyflavone-7-O-(6''-O-p-coumaroyl)-β-D-glucopyranoside (3), have been isolated from Bidens frondosa together with fifty-three known compounds 4-56. The structures of these compounds were established by spectroscopic methods. mainly ESIMS, 1D- and 2D-NMR spectroscopic data. and comparison with literature data. Compounds 1-34, 36, 39, 43, 47, 51, and 52 were tested for inhibition of nuclear factor kappa B (NF-κB) in 293-NF-κB-luciferase report cell line induced by lipopolysaccharide (LPS), and compounds 1, 2, 3, 9, 15, 21, 24 and 51 were tested for the production of TNF-α, IL-1β, IL-6, IL-10 in RAW 264.7 macrophages induced by LPS. In conclusion, the isolated compounds 1, 2, 3, 9, 15, 21, 24 and 51 exhibited significant activity in anti-inflammatory activity assays.

Chemical variability and antioxidant activity of Limbarda crithmoides L. essential oil from Corsica

The chemical compositions of 25 Corsican Limbarda crithmoides ssp. longifolia essential oils were investigated for the first time using GC-FID, GC/MS, and NMR analyses. Altogether, 65 compounds were identified, accounting for 90.0-99.3% of the total oil compositions. The main components were p-cymene (1; 15.1-34.6%), 3-methoxy-p-cymenene (4; 11.8-28.5%), 2,5-dimethoxy-p-cymenene (5; 5.9-16.4%), thymol methyl ether (6; 1.3-14.9%), α-phellandrene (2; 0.9-11.9%), and α-pinene (3; 0.2-13.4%). The chemical variability of the Corsican oil samples was studied using multivariate statistical analysis, which allowed the discrimination of two main clusters. A direct correlation between the water salinities of the plant locations and the chemical compositions of the L. crithmoides essential oils was evidenced. Indeed, essential oils rich in 1 (30.4-34.6%) were found in samples growing in the wetlands of the southern oriental coast, which exhibit high salinity levels (24.4±0.2-33.9±0.2 ppt), and essential oils with lower contents of 1 (15.1-27.3%) were isolated form samples growing in the wetlands of northern Corsica, which exhibit lower salinity levels (10.90±0.20-15.47±0.15 ppt). The antioxidant potential of L. crithmoides essential oil was also investigated, by assessing the DPPH(.) - and ABTS(.+) -scavenging activities and the reducing power of ferric ions, and was found to be interesting. Moreover, using bioassay-guided fractionation of the essential oil, a higher antioxidant activity was obtained for the oxygenated fraction and both ester and alcohol subfractions.

The genus Inula and their metabolites: from ethnopharmacological to medicinal uses

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Inula comprises more than one hundred species widespread in temperate regions of Europe and Asia. Uses of this genus as herbal medicines have been first recorded by the Greek and Roman ancient physicians. In the Chinese Pharmacopoeia, from the 20 Inula spp. distributed in China, three are used as Traditional Chinese medicines, named Tumuxiang, Xuanfuhua and Jinfeicao. These medicines are used as expectorants, antitussives, diaphoretics, antiemetics, and bactericides. Moreover, Inula helenium L. which is mentioned in Minoan, Mycenaean, Egyptian/Assyrian pharmacotherapy and Chilandar Medical Codex, is good to treat neoplasm, wound, freckles and dandruff. Many other Inula spp. are used in Ayurvedic and Tibetan traditional medicinal systems for the treatment of diseases such as bronchitis, diabetes, fever, hypertension and several types of inflammation. This review is a critical evaluation of the published data on the more relevant ethnopharmacological and medicinal uses of Inula spp. and on their metabolites biological activities. This study allows the identification of the ethnopharmacological knowledge of this genus and will provide insight into the emerging pharmacological applications of Inula spp. facilitating the prioritirization of future investigations. The corroboration of the ethnopharmacological applications described in the literature with proved biological activities of Inula spp. secondary metabolites will also be explored.

MATERIALS AND METHODS

The major scientific databases including ScienceDirect, Medline, Scopus and Web of Science were queried for information on the genus Inula using various keyword combinations, more than 180 papers and patents related to the genus Inula were consulted. The International Plant Name Index was also used to confirm the species names.

RESULTS

Although the benefits of Inula spp. are known for centuries, there are insufficient scientific studies to certify it. Most of the patents are registered by Chinese researchers, proving the traditional use of these plants in their country. Although a total of sixteen Inula species were reported in the literature to have ethnopharmacological applications, the species Inula cappa (Buch.-Ham. ex D.Don) DC., Inula racemosa Hook.f., Inula viscosa (L.) Aiton [actually the accepted name is Dittrichia viscosa (L.) Greuter], Inula helenium, Inula britannica L. and Inula japonica Thunb. are the most frequently cited ones since their ethnopharmacological applications are vast. They are used to treat a large spectrum of disorders, mainly respiratory, digestive, inflammatory, dermatological, cancer and microbial diseases. Fifteen Inula spp. crude extracts were investigated and showed interesting biological activities. From these, only 7 involved extracts of the reported spp. used in traditional medicine and 6 of these were studied to isolate the bioactive compounds. Furthermore, 90 bioactive compounds were isolated from 16 Inula spp. The characteristic compounds of the genus, sesquiterpene lactones, are involved in a network of biological effects, and in consequence, the majority of the experimental studies are focused on these products, especially on their cytotoxic and anti-inflammatory activities. The review shows the chemical composition of the genus Inula and presents the pharmacological effects proved by in vitro and in vivo experiments, namely the cytotoxic, anti-inflammatory (with focus on nitric oxide, arachidonic acid and NF-κB pathways), antimicrobial, antidiabetic and insecticidal activities.

CONCLUSIONS

Although there are ca. 100 species in the genus Inula, only a few species have been investigated so far. Eight of the sixteen Inula spp. with ethnopharmacological application had been subjected to biological evaluations and/or phytochemical studies. Despite Inula royleana DC. and Inula obtusifolia A. Kerner are being used in traditional medicine, as far as we are aware, these species were not subjected to phytochemical or pharmacological studies. The biological activities exhibited by the compounds isolated from Inula spp., mainly anti-inflammatory and cytotoxic, support some of the described ethnopharmacological applications. Sesquiterpene lactone derivatives were identified as the most studied class, being britannilactone derivatives the most active ones and present high potential as anti-inflammatory drugs, although, their pharmacological effects, dose-response relationship and toxicological investigations to assess potential for acute or chronic adverse effects should be further investigated. The experimental results are promising, but the precise mechanism of action, the compound or extract toxicity, and the dose to be administrated for an optimal effect need to be investigated. Also human trials (some preclinical studies proved to be remarkable) should be further investigated. The genus Inula comprises species useful not only in medicine but also in other domains which makes it a high value-added plant.

Chemical constituents from Tribulus terrestris and screening of their antioxidant activity

Two oligosaccharides (1,2) and a stereoisomer of di-p-coumaroylquinic acid (3) were isolated from the aerial parts of Tribulus terrestris along with five known compounds (4-8). The structures of the compounds were established as O-β-D-fructofuranosyl-(2→6)-α-D-glucopyranosyl-(1→6)-β-D-fructofuranosyl-(2→6)-β-D-fructofuranosyl-(2→1)-α-D-glucopyranosyl-(6→2)-β-D-fructofuranoside (1), O-α-D-glucopyranosyl-(1→4)-α-D-glucopyranosyl-(1→4)-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside (2), 4,5-di-p-cis-coumaroylquinic acid (3) by different spectroscopic methods including 1D NMR ((1)H, (13)C and DEPT) and 2D NMR (COSY, TOCSY, HMQC and HMBC) experiments as well as ESI-MS analysis. This is the first report for the complete NMR spectral data of the known 4,5-di-p-trans-coumaroylquinic acid (4). The antioxidant activity represented as DPPH free radical scavenging activity was investigated revealing that the di-p-coumaroylquinic acid derivatives possess potent antioxidant activity so considered the major constituents contributing to the antioxidant effect of the plant.