Iridoids from Borreria verticillata

Iridoid Derivatives as Anticancer Agents: An Updated Review from 1970-2022

The rise of cancer cases has coincided with the urgent need for the development of potent chemical entities and/or modification of existing commodities to improve their efficacy. Increasing evidence suggests that cancer remains one of the leading causes of death globally, with colon cancer cases alone likely to rise exponentially by 2030. The exponential rise in cancer prevalence is largely attributable to the growing change toward a sedentary lifestyle and modern diets, which include genetically modified foods. At present, the prominent treatments for cancer are chemotherapy, surgery, and radiation. Despite slowing cancer progression, these treatments are known to have devastating side effects that may deteriorate the health of the patient, thus, have a low risk-benefit ratio. In addition, many cancer drugs have low bioavailability, thereby limiting their therapeutic effects in cancer patients. Moreover, the drastic rise in the resistance of neoplastic cells to chemotherapeutic agents is rendering the use of some drugs ineffective, thereby signaling the need for more anticancer chemical entities. As a result, the use of natural derivatives as anticancer agents is gaining considerable attention. Iridoids have the potential to form conjugates with other anticancer, antidiabetic, antileishmanial, and antimalarial drugs, which synergistically have the potential to increase their effects. Published studies have identified the role of iridoids, which, if fully explored, may result in cheaper and less toxic alternative/adjuvant cancer drugs. The subject of this article is natural and synthetic iridoid derivatives and their potential therapeutic roles as anticancer agents.

Chemotaxonomy and Antibacterial Activity of the Extracts and Chemical Constituents of Psychotria succulenta Hiern. (Rubiaceae)

The use of natural products for medicinal purposes is becoming more and more common nowadays, as evidenced by the presence in plants of secondary metabolites with different potentials such as antioxidant and antibacterial properties. We evaluated in this work the antimicrobial activities of the extracts and some isolated compounds from the seeds of Psychotria succulenta Hiern. (Rubiaceae), a Cameroonian medicinal plant traditionally used to cure microbial infections. The ethanol extract was prepared by maceration and extracted with ethyl acetate and n-butanol. The EtOAc (m = 168 g) and n-BuOH (m = 20 g) extracts were further fractionated by silica gel column chromatography to isolation of compounds. Their structures were elucidated by spectroscopic analysis and by comparison with published data. The antibacterial activity of extracts and compounds was assessed by evaluating the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against pathogenic bacteria. Thirteen compounds including four alkaloids (veprisine (1), naucleofficine III (2), vepridimerine B (3), and vepridimerine C (4)), three triterpenes (barbinervic acid (5), 3-O-α-L-rhamnopyranosyl quinovic acid (6), and oleanolic acid (7)), one steroid (β-sitosterol-3-O-β-D-glucopyranoside (8)), four phenolic compounds (scopoletin (9), gallic acid (10), quercetin-3-O-β-D-glucopyranoside (11), and kaempferol 3-O-α-L-rhamnopyranoside-7-O-α-L-rhamnopyranoside (12)), and one iridoid (borreriagenin (13)) were isolated from the EtOAc and n-BuOH extracts. These compounds were identified by 1D and 2D NMR combined analysis as well as by melting point comparison. The EtOH, EtOAc, and n-BuOH extracts exhibited significant antibacterial activities (MIC = 32‐128 μg/mL; MBC = 64‐256 μg/mL) against Staphylococcus aureus (Gram-positive bacterium), Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumonia (Gram-negative bacteria). Among the isolated compounds, scopoletin (9) showed a moderate activity against Klebsiella pneumoniae with MIC and MBC values of 16 μg/mL and 32 μg/mL, respectively. It appears that, chemotaxonomically, some of the isolated compounds have already been obtained from the genus Psychotria but to the best of our knowledge, this is the first report on the phytochemical investigation of P. succulenta. Although many other studies need to be achieved, our results support the use of P. succulenta in traditional medicine to cure infectious diseases particularly those caused by the tested bacteria.

Polycyclic Phenol Derivatives from the Leaves of Spermacoce latifolia and Their Antibacterial and α-Glucosidase Inhibitory Activity

Three new polycyclic phenol derivatives, 2-acetyl-4-hydroxy-6H-furo [2,3-g]chromen-6-one (1), 2-(1′,2′-dihydroxypropan-2′-yl)-4-hydroxy-6H-furo [2,3-g][1]benzopyran-6-one (2) and 3,8,10-trihydroxy-4,9-dimethoxy-6H-benzo[c]chromen-6-one (8), along with seven known ones (3–7, 9 and 10) were isolated for the first time from the leaves of Spermacoce latifolia. Their structures were determined by spectroscopic analysis and comparison with literature-reported data. These compounds were tested for their in vitro antibacterial activity against four Gram-(+) bacteria: Staphyloccocus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), Bacillus cereus (BC), Bacillus subtilis (BS), and the Gram-(−) bacterium Escherichia coli. Compounds 1, 2, 5 and 8 showed antibacterial activity toward SA, BC and BS with MIC values ranging from 7.8 to 62.5 µg/mL, but they were inactive to MRSA. Compound 4 not only showed the best antibacterial activity against SA, BC and BS, but it further displayed significant antibacterial activity against MRSA (MIC 1.95 µg/mL) even stronger than vancomycin (MIC 3.9 µg/mL). No compounds showed inhibitory activity toward E. coli. Further bioassay indicated that compounds 1, 4, 5, 6, 8 and 9 showed in vitro α-glucosidase inhibitory activity, among which compound 9 displayed the best α-glucosidase inhibitory activity with IC₅₀ value (0.026 mM) about 15-fold stronger than the reference compound acarbose (IC₅₀ 0.408 mM). These results suggested that compounds 4, 8 and 9 were potentially highly valuable compounds worthy of consideration to be further developed as an effective anti-MRSA agent or effective α-glucosidase inhibitors, respectively. In addition, the obtained data also supported that S. latifolia was rich in structurally diverse bioactive compounds worthy of further investigation, at least in searching for potential antibiotics and α-glucosidase inhibitors.

Biological insights and NMR metabolic profiling of different extracts of Spermacoce verticillata (L.) G. Mey

Spermacoce verticillata (L.) G. Mey. is commonly used in the folk medicine by various cultures to manage common diseases. Herein, the chemical and biological profiles of S. verticillata were studied in order to provide a comprehensive characterization of bioactive compounds and also to highlight the therapeutic properties. The in vitro antioxidant activity using free-radical scavenging, phosphomolybdenum, ferrous-ion chelating and reducing power assays, and the inhibitory activity against key enzymes such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), tyrosinase, α-amylase and α-glucosidase of S. verticillata extracts (dichloromethane, ethyl acetate, methanol and water) were investigated. The highest total phenolic and flavonoid content were observed in the methanolic and aqueous extracts. Exhaustive 2DNMR investigation has revealed the presence of rutin, ursolic and oleanoic acids. The methanolic extract, followed by aqueous extract have showed remarkable free radical quenching and reducing ability, while the dichloromethane extract was the best source of metal chelators. The tested extracts showed notable inhibitory activity against cholinesterases (AChE: 1.63 - 4.99 mg GALAE/g extract and BChE: 12.40 - 15.48 mg GALAE/g extract) and tyrosinase (60.85 - 159.64 mg KAE/g extract). No inhibitory activity was displayed by ethyl acetate and aqueous extracts against BChE and tyrosinase, respectively. All the tested extracts showed modest α-amylase inhibitory activity, while only the ethyl acetate and aqueous extracts were potent against α-glycosidase. This study further validates the use of S. verticillata in the traditional medicine, while advocating for further investigation for phytomedicine development.

A review on Borreria verticillata: A potential bionematicide, channeling its significant antimicrobial activity against root-knot nematodes

Phytopesticides are human-friendly beside been easily accessible and bio-degradable, are therefore environmentally friendly compared to the synthetic pesticides which huge adverse effects on human, animals and the ecosystem. Plants are large reservoir of secondary metabolites largely untapped or under-tapped for use as pesticides. One problem associated with this is to identify plants which can be assessed and further exploited for this use. Borreria verticillata belongs to Rubiaceae, it is native to South Americas but gained popularity globally. It is known as a weed, showing resistance to many synthetic pesticides and can be grown on a wide range of soil types. B. verticillata is used traditionally against skin diseases such as eczema, infectious dermatitis and scabies. Its antimicrobial application is large and efficient as revealed by most authors. This article inclines to propose and offer current studies with information on the various application of this plant species against various microorganisms, thereby extending its use against plant parasitic nematodes which cause severe yield losses to numerous agricultural crops. Most search engines, journals and dissertation search engines i.e. Google scholar, pubmed, sciencedirect, scopus, web of science, springer, elsevier, like Open-thesis, OATD, ProQuest and EthOs were queried by employing titles such as B. verticillata, Borreria verticillata and biological activity of B. verticillata. The most synonymous name was queried too i.e. Spermacoce verticillata. This review suggests a main point about this resistant weed i.e. its significant antimicrobial activity. It further emphases the need exploits this useful effect against nematodes since they are microorganisms. Phytochemistry of the B. verticillata was gathered in this study and the compounds isolated from the plant i.e. terpenes, iridoids, flavonoids and alkaloids (29 compounds) further provide a basis for a significant antihelmintic effect. The review concludes on the need to extends its antimicrobial activity to sustainable agriculture. Since it is a very common plant in Nigeria, it is easily accessible to farmer protect their cultivations from plant-parasitic nematode attacks.

Estrogen and Thyroid Hormone Receptor Activation by Medicinal Plants from Bahia, Brazil

Background: A number of medicinal plants are traditionally used for metabolic disorders in Bahia state, Brazil. The aim of this study was to evaluate the estrogen receptor (ER) and thyroid receptor (TR) activation of crude extracts prepared from 20 plants. Methods: Species were extracted and assayed for receptor activation through both ER and TR gene-reporter assays, using 17β-estradiol and triiodothyronine (T3), respectively, as the positive controls. Results: Cajanus cajan (Fabaceae), Abarema cochliacarpus (Fabaceae), and Borreria verticillata (Rubiaceae) were able to activate ER as much as the positive control (17β-estradiol). These three plant species were also assayed for TR activation. At the concentration of 50 µg/mL, C. cajans exerted the highest positive modulation on TR, causing an activation of 59.9%, while B. verticillata and A. cochliacarpus caused 30.8% and 23.3%, respectively. Conclusions: Our results contribute towards the validation of the traditional use of C. cajans, B. verticillata, and A. cochliacarpus in the treatment of metabolic disorders related to ER and TR functions. The gene-reporter assay was proven effective in screening crude plant extracts for ER/TR activation, endorsing this methodology as an important tool for future bioprospection studies focused on identifying novel starting molecules for the development of estrogen and thyroid agonists.

A new anthraquinone and a new naphthoquinone from the whole plant of Spermacoce latifolia

A phytochemical study on the whole plant of Spermacoce latifolia led to the isolation of a new anthraquinone, 1,2,6-trihydroxy-5-methoxy-9,10-anthraquinone (1), and a new naphthoquinone, (2R)-6-hydroxy-7-methoxy-dehydroiso-α-lapachone (2), together with three known anthraquinones (3-5). Their structures were established on the basis of detailed spectroscopic analysis, including one- and two-dimensional NMR, ESI-MS, and HR-ESI-MS techniques. All the compounds were isolated from S. latifolia for the first time. Compounds 1, 2, 4, and 5 showed significant antibacterial activity toward Bacillus subtilis with MIC values ranging from 0.9 to 31.2 μg/ml, and compound 4 aslo exhibited antibacterial activity against Bacillus cereus with a MIC value 62.5 μg/ml. Compound 1 was further revealed to show significant in vitro α-glucosidase inhibitory activity with IC₅₀ value of 0.653 mM.

Antinociceptive Activity of Borreria verticillata: In vivo and In silico Studies

Borreria verticillata (L.) G. Mey. known vassourinha has antibacterial, antimalarial, hepatoprotective, antioxidative, analgesic, and anti-inflammatory, however, its antinociceptive action requires further studies. Aim of the study evaluated the antinociceptive activity of B. verticillata hydroalcoholic extract (EHBv) and ethyl acetate fraction (FAc) by in vivo and in silico studies. In vivo assessment included the paw edema test, writhing test, formalin test and tail flick test. Wistar rats and Swiss mice were divided into 6 groups and given the following treatments oral: 0.9% NaCl control group (CTRL), 10 mg/kg memantine (MEM), 10 mg/kg indomethacin (INDO), 500 mg/kg EHBv (EHBv 500), 25 mg/kg FAc (FAc 25) and 50 mg/kg FAc (FAc 50). EHBv, FAc 25 and 50 treatments exhibited anti-edematous and peripheral antinociceptive effects. For in silico assessment, compounds identified in FAc were subjected to molecular docking with COX-2, GluN1a and GluN2B. Ursolic acid (UA) was the compound with best affinity parameters (binding energy and inhibition constant) for COX-2, GluN1a, GluN2B, and was selected for further analysis with molecular dynamics (MD) simulations. In MD simulations, UA exhibited highly frequent interactions with residues Arg120 and Glu524 in the COX-2 active site and NMDA, whereby it might prevent COX-2 and NMDA receptor activation. Treatment with UA 10 mg/Kg showed peripheral and central antinociceptive effect. The antinociceptive effect of B. verticillata might be predominantly attributed to peripheral actions, including the participation of anti-inflammatory components. Ursolic acid is the main active component and seems to be a promising source of COX-2 inhibitors and NMDA receptor antagonists.

A New Iridoid from the Aerial Parts of Hedyotis Pilulifera

A new iridoid, 10-acetylborreriagenin (1), and five known iridoid glycosides (2–6), were isolated from the aerial parts of Hedyotis pilulifera. Their structures were elucidated by spectral analyses, including 1D- and 2D-NMR, and HR-ESI-MS, and comparisons with the NMR data reported in the literature. The isolated compounds 1–6 were tested against six bacterial species. Among them, 10-acetylborreriagenin (1) showed antibacterial activity against Staphylococcus aureus, with an MIC value of 100 μg/mL.

Cytotoxicity of 91 Kenyan indigenous medicinal plants towards human CCRF-CEM leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Plants from Kenyan flora are traditionally used against many ailments, including cancer and related diseases. Cancer is characterized as a condition with complex signs and symptoms. Recently there are recommendations that ethnopharmacological usages such as immune and skin disorders, inflammatory, infectious, parasitic and viral diseases should be taken into account when selecting plants that treat cancer.

AIM

The present study was aimed at investigating the cytotoxicity of a plethora of 145 plant parts from 91 medicinal plants, most of which are used in the management of cancer and related diseases by different communities in Kenya, against CCRF-CEM leukemia cell line.

MATERIALS AND METHODS

Extracts from different plant parts (leaves, stems, stem bark, roots, root barks, aerial parts and whole herb) were obtained by cold percolation using different solvent systems, such as (1:1v/v) dichloromethane (CH2Cl2) and n-hexane (1), methanol (MeOH) and CH2Cl2 (2); neat MeOH (3), 5% H2O in MeOH (4) and with ethanol (EtOH, 5); their cytotoxicities were determined using the resazurin reduction assay against CCRF-CEM cells.

RESULTS

At a single concentration of 10μg/mL, 12 out of 145 extracts exhibited more than 50% cell inhibition. These include samples from the root bark of Erythrina sacleuxii (extracted with 50% n-hexane-CH2Cl2), the leaves of Albizia gummifera, and Strychnos usambarensis, the stem bark of Zanthoxylum gilletii, Bridelia micrantha, Croton sylvaticus, and Albizia schimperiana; the root bark of Erythrina burttii and E. sacleuxii (extracted with 50% CH2Cl2-MeOH), the stem bark of B. micrantha and Z. gilletii (extracted using 5% MeOH-H2O) and from the berries of Solanum aculeastrum (extracted with neat EtOH). The EtOH extract of the berries of S. aculeastrum and A. schimperiana stem bark extract displayed the highest cytotoxicity towards leukemia CCRF-CEM cells, with IC50 values of 1.36 and 2.97µg/mL, respectively. Other extracts having good activities included the extracts of the stem barks of Z. gilletii and B. micrantha and leaves of S. usambarensis with IC50 values of 9.04, 9.43 and 11.09µg/mL, respectively.

CONCLUSIONS

The results of this study provided information related to the possible use of some Kenyam medicinal plants, and mostly S. aculeastrum, A. schimperiana, C. sylvaticus, Z. gilletii, B. micrantha and S. usambarensis in the treatment of leukemia. The reported data helped to authenticate the claimed traditional use of these plants. However, most plants are used in combination as traditional herbal concoctions. Hence, the cytotoxicity of corresponding plant combinations should be tested in vitro to authenticate the traditional medical practitioners actual practices.

Practical Isolation of Asperuloside from Coprosma quadrifida via Rapid Pressurised Hot Water Extraction

The valuable glycoside asperuloside was efficiently isolated in multigram quantities from Coprosma quadrifida employing a recently developed rapid pressurised hot water extraction (PHWE) method that utilises an unmodified household espresso machine. This study represents the first time C. quadrifida has been extracted and its major chemical components isolated and analysed. Our findings reveal that this species is a rich source of asperuloside (7.0 % yield w/w). Significantly, this represents one of the highest yields obtained of this glycoside from a Coprosma species, and the entire Rubiaceae family more generally.

An iridoid glucoside and the related aglycones from Cornus florida

A new iridoid glucoside, cornusoside A (1), and four new natural product iridoid aglycones, cornolactones A-D (2-5), together with 10 known compounds were isolated from the leaves of Cornus florida. The structures of compounds 1-5 were established by interpretation of their spectroscopic data. Cornolactone B (3) is the first natural cis-fused tricyclic dilactone iridoid containing both a five- and a six-membered lactone ring. A biosynthesis pathway is proposed for cornolactones C (4) and D (5), the C-6 epimers of compounds 1-3.

Two Novel Iridoids from Morinda longifolia

Six secondary metabolites, including two novel iridoids, longifolides A (1) and B (2), were isolated by various chromatographic methods from a methanol extract of branches and leaves of Morinda longifolia Craib. The structures of the compounds were determined on the basis of NMR spectroscopic (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY) and FTICR-MS data, as well as by comparison of them with literature values.

Revision of the Structures of Citrifolinin A, Citrifolinoside, Yopaaoside A, Yopaaoside B, and Morindacin, Iridoids from Morinda citrifolia L. and Morinda coreia Ham

[Structure: see text] Citrifolin A was revised to dehydromethoxygaertneroside (2). Citrifolinoside and yopaaoside A were found to be identical, and their structures were revised to the new structure dehydroepoxymethoxygaertneroside (5). Yopaaoside B was revised to citrifolinoside A (9), and morindacin was revised to borreriagenin (11).