Phytochemical Constituents of Annona reticulata and their Cytotoxic Activity

2020 ◽  
Vol 17 (3) ◽  
pp. 206-210
Author(s):  
Ty Viet Pham ◽  
Thang Quoc Le ◽  
Anh Tuan Le ◽  
Hung Quoc Vo ◽  
Duc Viet Ho
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Structural Determination ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
Phytochemical Constituents ◽  
First Time ◽  
Annona Reticulata

A phytochemical investigation of the leaves of Annona reticulata led to the isolation and structural determination of β-sitosterol (1), ent-pimara-8(14),15-dien-19-oic acid (2), ent-pimara- 8(14),15-dien-19-ol (3), quercetin (4), quercetin 3-O-α-L-arabinopyranoside (5), and a mixture of quercetin 3-O-β-D-galactopyranoside (6a) and quercetin 3-O-β-D-glucopyranoside (6b). Of these, compounds 2 and 3 were isolated from the genus Annona for the first time. Compound 3 showed strong cytotoxicity against SK-LU-1 and SW626 cell lines with IC50 values of 17.64 ± 1.07 and 19.79 ± 1.41 μg mL-1, respectively.

scholarly journals Labdane and Abietane Diterpenoids from Juniperus oblonga and Their Cytotoxic Activity

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1561 ◽  
Author(s):  
Qiao ◽  
Khutsishvili ◽  
Alizade ◽  
Atha ◽  
Borris
Keyword(s):  
Cell Lines ◽  
Human Tumor ◽  
2D Nmr ◽  
Human Tumor Cell Lines ◽  
Abietane Diterpenoids ◽  
Whole Plant ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
First Time ◽  
Mcf 7

A phytochemical investigation of the whole plant of Juniperus oblonga led to the isolationof one previously undescribed labdane diterpenoid, (4R,5S,9S,10R)‐13‐des‐ethyl‐13‐oxolabda‐8(17),11E‐dien‐19‐oic acid (1), together with nine known diterpenoids (2–3, 6–12), two lignans (4, 5),and a coumarin (13). The structures of all the compounds were elucidated on the basis ofspectrometric data, primarily one‐dimensional (1D)‐ and two‐dimensional (2D)‐NMR and massspectrometry. Electronic circular dichroism (ECD) calculations determined the absoluteconfiguration of 1. In addition, the isolated compounds were evaluated for their cytotoxic activityagainst three human tumor cell lines (HepG2, MCF‐7, and HeLa). 6,12‐Dihydroxyabieta‐5,8,11,13‐tetraen‐7‐one (6) showed moderate cytotoxicity against all three cell lines with IC50 values rangingfrom 24.41 μM to 58.39 μM and trilobinone (10) showed weaker activity with IC50 values rangingfrom 56.93 μM to 79.98 μM. None of the isolated diterpenoids have been previously reported fromJuniperus oblonga, and five compounds are here reported from the genus Juniperus for the first time.

scholarly journals Chemical constituents and cytotoxicity of Aspidistra letreae

2020 ◽  
Vol 129 (1B) ◽  
pp. 31-39
Author(s):  
Duc Viet Ho ◽  
Hanh Nhu Thi Hoang ◽  
Khue Minh Vo ◽  
Anh Tuan Le ◽  
Hoai Thi Nguyen
Keyword(s):  
Human Cancer ◽  
Chemical Constituents ◽  
Hep G2 ◽  
Human Cancer Cell Lines ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
Reported Data ◽  
Whole Plants ◽  
First Time

A phytochemical investigation of whole Aspidistra letreae plants led to the isolation of 2H-chromen-2-one (1), α-tocopherol (2), (E)-phytol (3), asparenydiol (4) and (25S)-spirost-1β,3α,5β-triol (5). Their structures were determined on the basis of NMR spectral evidences and in comparison with the reported data. Of these, asparenydiol (4) was isolated from the genus Aspidistra for the first time. This is also the first report on the separation and structural determination of (25S)-spirost-1β,3α,5β-triol (5) as a pure compound. The methanol extract from the whole plants of Aspidistra letreae exhibits moderate cytotoxicity against the LU-1, HeLa, MDA-MB-231, Hep-G2, and MKN-7 human cancer cell lines with IC50 values ranging from 52.58 ± 3.65 to 64.78 ± 4.89 μg/mL.

scholarly journals Determination of Cytotoxic Activity of Sanguinaria canadensis Extracts against Human Melanoma Cells and Comparison of Their Cytotoxicity with Cytotoxicity of Some Anticancer Drugs

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1738
Author(s):  
Tomasz Tuzimski ◽  
Anna Petruczynik ◽  
Tomasz Plech ◽  
Barbara Kaproń ◽  
Anna Makuch-Kocka ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Anticancer Drugs ◽  
Plant Material ◽  
Melanoma Cells ◽  
Human Melanoma ◽  
Sanguinaria Canadensis ◽  
Human Melanoma Cells ◽  
Ic50 Values

Melanoma is an enormous global health burden, and should be effectively addressed with better therapeutic strategies. Therefore, new therapeutic agents are needed for the management of this disease. The aim of this study was the investigation of cytotoxic activity of some isoquinoline alkaloid standards and extracts obtained from Sanguinaria canadensis—collected before, during, and after flowering—against three different human melanoma cells (A375, G361, SK-MEL-3). The cytotoxicity of these extracts was not previously tested on these melanoma cell lines. Determination of alkaloid contents was performed by HPLC-DAD using Polar RP column and mobile phase containing acetonitrile, water, and 1-butyl-3-methylimidazolium tetrafluoroborate. The cytotoxicity of alkaloid standards was investigated by determination of cell viability and calculation of IC50 values. Significant differences were observed in the alkaloids content and cytotoxic activity of the extracts, depending on the season of collection of the plant material. In the Sanguinaria canadensis extracts high contents of sanguinarine (from 4.8543 to 9.5899 mg/g of dry plant material) and chelerythrine (from 42.7224 to 6.8722 mg/g of dry plant material) were found. For both of these alkaloids, very high cytotoxic activity against the tested cell lines were observed. The IC50 values were in the range of 0.11–0.54 µg/mL for sanguinarine and 0.14 to 0.46 µg/mL for chelerythrine. IC50 values obtained for Sanguinaria canadensis extracts against all tested cell lines were also very low (from 0.88 to 10.96 µg/mL). Cytotoxic activity of alkaloid standards and Sanguinaria canadensis extracts were compared with the cytotoxicity of anticancer drugs—etoposide, cisplatin, and hydroxyurea. In all cases except the one obtained for cisplatin against A375, which was similar to that obtained for Sanguinaria canadensis after flowering against the same cell line, IC50 values obtained for anticancer drugs were higher than the IC50 values obtained for sanguinarine, chelerythrine, and Sanguinaria canadensis extracts. Our results showed that Sanguinaria canadensis extracts and isoquinoline alkaloids, especially sanguinarine and chelerythrine, could be recommended for further in vivo experiments in order to confirm the possibility of their application in the treatment of human melanomas.

scholarly journals Benzylated Dihydroflavones and Isoquinoline-Derived Alkaloids from the Bark of Diclinanona calycina (Annonaceae) and Their Cytotoxicities

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3714
Author(s):  
Emmanoel V. Costa ◽  
Liviane do N. Soares ◽  
Jamal da Silva Chaar ◽  
Valdenizia R. Silva ◽  
Luciano de S. Santos ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
2D Nmr ◽  
Cytotoxic Activities ◽  
2D Nmr Spectroscopy ◽  
Cancerous Cell ◽  
Ic50 Value ◽  
Ic50 Values ◽  
Low Cytotoxicity ◽  
First Time

Diclinanona calycina R. E. Fries popularly known as “envira”, is a species of the Annonaceae family endemic to Brazil. In our ongoing search for bioactive compounds from Annonaceae Amazon plants, the bark of D. calycina was investigated by classical chromatography techniques that yielded thirteen compounds (alkaloids and flavonoids) described for the first time in D. calycina as well as in the genus Diclinanona. The structure of these isolated compounds were established by extensive analysis using 1D/2D-NMR spectroscopy in combination with MS. The isolated alkaloids were identified as belonging to the subclasses: simple isoquinoline, thalifoline (1); aporphine, anonaine (2); oxoaporphine, liriodenine (3); benzyltetrahydroisoquinolines, (S)-(+)-reticuline (4); dehydro-oxonorreticuline (3,4-dihydro-7-hydroxy-6-methoxy-1-isoquinolinyl)(3-hydroxy-4-methoxyphenyl)-methanone) (5); (+)-1S,2R-reticuline Nβ-oxide (6); and (+)-1S,2S-reticuline Nα-oxide (7); tetrahydroprotoberberine, coreximine (8); and pavine, bisnorargemonine (9). While the flavonoids belong to the benzylated dihydroflavones, isochamanetin (10), dichamanetin (11), and a mixture of uvarinol (12) and isouvarinol (13). Compound 5 is described for the first time in the literature as a natural product. The cytotoxic activity of the main isolated compounds was evaluated against cancer and non-cancerous cell lines. Among the tested compounds, the most promising results were found for the benzylated dihydroflavones dichamanetin (10), and the mixture of uvarinol (12) and isouvarinol (13), which presented moderate cytotoxic activity against the tested cancer cell lines (<20.0 µg·mL−1) and low cytotoxicity against the non-cancerous cell line MRC-5 (>25.0 µg·mL−1). Dichamanetin (11) showed cytotoxic activity against HL-60 and HCT116 with IC50 values of 15.78 µg·mL−1 (33.70 µmol·L−1) and 18.99 µg·mL−1 (40.56 µmol·L−1), respectively while the mixture of uvarinol (12) and isouvarinol (13) demonstrated cytotoxic activity against HL-60, with an IC50 value of 9.74 µg·mL−1, and HCT116, with an IC50 value of 17.31 µg·mL−1. These cytotoxic activities can be attributed to the presence of one or more hydroxybenzyl groups present in these molecules as well as the position in which these groups are linked. The cytotoxic activities of reticuline, anonaine and liriodenine have been previously established, with liriodenine being the most potent compound.

scholarly journals Mammalian Arginase Inhibitory Activity of Methanolic Extracts and Isolated Compounds from Cyperus Species

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1694
Author(s):  
Kamel Arraki ◽  
Perle Totoson ◽  
Alain Decendit ◽  
Andy Zedet ◽  
Justine Maroilley ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Methanolic Extract ◽  
Significant Inhibition ◽  
Isolation And Identification ◽  
Vasorelaxant Effect ◽  
Methanolic Extracts ◽  
Phytochemical Investigation ◽  
Ic50 Values ◽  
First Time

Polyphenolic enriched extracts from two species of Cyperus, Cyperus glomeratus and Cyperus thunbergii, possess mammalian arginase inhibitory capacities, with the percentage inhibition ranging from 80% to 95% at 100 µg/mL and 40% to 64% at 10 µg/mL. Phytochemical investigation of these species led to the isolation and identification of two new natural stilbene oligomers named thunbergin A-B (1–2), together with three other stilbenes, trans-resveratrol (3), trans-scirpusin A (4), trans-cyperusphenol A (6), and two flavonoids, aureusidin (5) and luteolin (7), which were isolated for the first time from C.thunbergii and C. glomeratus. Structures were established on the basis of the spectroscopic data from MS and NMR experiments. The arginase inhibitory activity of compounds 1–7 was evaluated through an in vitro arginase inhibitory assay using purified liver bovine arginase. As a result, five compounds (1, 4–7) showed significant inhibition of arginase, with IC50 values between 17.6 and 60.6 µM, in the range of those of the natural arginase inhibitor piceatannol (12.6 µM). In addition, methanolic extract from Cyperus thunbergii exhibited an endothelium and NO-dependent vasorelaxant effect on thoracic aortic rings from rats and improved endothelial dysfunction in an adjuvant-induced arthritis rat model.

scholarly journals Asperienes A–D, Bioactive Sesquiterpenes from the Marine-Derived Fungus Aspergillus flavus

Marine Drugs ◽  
2019 ◽  
Vol 17 (10) ◽  
pp. 550 ◽  
Author(s):  
Yun-Feng Liu ◽  
Yu-Fei Yue ◽  
Li-Xi Feng ◽  
Hua-Jie Zhu ◽  
Fei Cao
Keyword(s):  
Cell Lines ◽  
Aspergillus Flavus ◽  
Solid Medium ◽  
Biological Activities ◽  
Antitumor Agent ◽  
Minor Components ◽  
Electronic Circular Dichroism ◽  
The Future ◽  
Ic50 Values ◽  
First Time

Marine-derived fungi of the genera Aspergillus could produce novel compounds with significant bioactivities. Among these fungi, the strain Aspergillus flavus is notorious for its mutagenic mycotoxins production. However, some minor components with certain toxicities from A. flavus have not been specifically surveyed and might have potent biological activities. Our investigation of the marine-derived fungus Aspergillus flavus CF13-11 cultured in solid medium led to the isolation of four C-6′/C-7′ epimeric drimane sesquiterpene esters, asperienes A–D (1–4). Their absolute configurations were assigned by electronic circular dichroism (ECD) and Snatzke’s methods. This is the first time that two pairs of C-6′/C-7′ epimeric drimane sesquiterpene esters have successfully been separated. Aperienes A–D (1–4) displayed potent bioactivities towards four cell lines with the IC50 values ranging from 1.4 to 8.3 μM. Interestingly, compounds 1 and 4 exhibited lower toxicities than 2 and 3 toward normal GES-1 cells, indicating more potential for development as an antitumor agent in the future.

scholarly journals Highly Substituted Benzophenone Aldehydes and Eremophilane Derivatives from the Deep-Sea Derived Fungus Phomopsis lithocarpus FS508

Marine Drugs ◽  
2018 ◽  
Vol 16 (9) ◽  
pp. 329 ◽  
Author(s):  
Jian-Lin Xu ◽  
Hong-Xin Liu ◽  
Yu-Chan Chen ◽  
Hai-Bo Tan ◽  
Heng Guo ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
A549 Cell ◽  
Marine Sediment ◽  
Deep Sea ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Naturally Occurring ◽  
Ic50 Values ◽  
New Compounds

Five new benzophenone derivatives named tenellones D–H (1–5), sharing a rare naturally occurring aldehyde functionality in this family, and a new eremophilane derivative named lithocarin A (7), together with two known compounds (6 and 8), were isolated from the deep marine sediment-derived fungus Phomopsis lithocarpus FS508. All of the structures for these new compounds were fully characterized and established on the basis of extensive spectroscopic interpretation and X-ray crystallographic analysis. Compound 5 exhibited cytotoxic activity against HepG-2 and A549 cell lines with IC50 values of 16.0 and 17.6 μM, respectively.

scholarly journals ­Chemical profiling and biological activity of Peperomia blanda (Jacq.) Kunth

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4839 ◽  
Author(s):  
Wafa M. Al-Madhagi ◽  
Najihah Mohd Hashim ◽  
Nasser A. Awad Ali ◽  
Abeer A. Alhadi ◽  
Siti Nadiah Abdul Halim ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Cell Lines ◽  
Cancer Cell ◽  
Radical Scavenging ◽  
Cancer Cell Lines ◽  
Cytotoxic Activities ◽  
Standard Drug ◽  
Chemical Profiling ◽  
First Time ◽  
Mcf 7

Background Peperomia belongs to the family of Piperaceae. It has different uses in folk medicine and contains rare compounds that have led to increased interest in this genus. Peperomia blanda (Jacq.) Kunth is used as an injury disinfectant by Yemeni people. In addition, the majority of Yemen’s population still depend on the traditional remedy for serious diseases such as cancer, inflammation and infection. Currently, there is a deficiency of scientific evidence with regards to the medicinal plants from Yemen. Therefore, this study was performed to assess the chemical profile and in vitro antioxidant and cytotoxic activities of P. blanda. Methods Chemical profiling of P. blanda was carried out using gas chromatography mass spectrometry (GCMS) followed by isolation of bioactive compounds by column chromatography. DPPH• and FRAP assays were used to evaluate antioxidant activity and the MTT assay was performed to estimate the cytotoxicity activity against three cancer cell lines, namely MCF-7, HL-60 and WEHI-3, and three normal cell lines, MCF10A, WRL-68 and HDFa. Results X-ray crystallographic data for peperomin A is reported for the first time here and N,N′-diphenethyloxamide was isolated for the first time from Peperomia blanda. Methanol and dichloromethane extracts showed high radical scavenging activity with an IC50 of 36.81 ± 0.09 µg/mL, followed by the dichloromethane extract at 61.78 ± 0.02 µg/mL, whereas the weak ferric reducing activity of P. blanda extracts ranging from 162.2 ± 0.80 to 381.5 ± 1.31 µg/mL were recorded. In addition, petroleum ether crude extract exhibited the highest cytotoxic activity against all the tested cancer cell lines with IC50 values of 9.54 ± 0.30, 4.30 ± 0.90 and 5.39 ± 0.34 µg/mL, respectively. Peperomin A and the isolated mixture of phytosterol (stigmasterol and β-sitosterol) exhibited cytotoxic activity against MCF-7 and WE-HI cell lines with an IC50 of (5.58 ± 0.47, 4.62 ± 0.03 µg/mL) and (8.94 ± 0.05, 9.84 ± 0.61 µg/mL), respectively, compared to a standard drug, taxol, that has IC50 values of 3.56 ± 0.34 and 1.90 ± 0.9 µg/mL, respectively. Conclusion The activities of P. blanda extracts and isolated compounds recorded in this study underlines the potential that makes this plant a valuable source for further study on anticancer and antioxidant activities.

scholarly journals Four New ent-Kaurane Diterpene Glycosides from Isodon henryi

Molecules ◽  
2019 ◽  
Vol 24 (15) ◽  
pp. 2736 ◽  
Author(s):  
Liu ◽  
Zhang ◽  
Wu ◽  
Chen ◽  
Li ◽  
...  
Keyword(s):  
Cell Lines ◽  
Human Cancer ◽  
Spectroscopic Methods ◽  
Human Cancer Cell ◽  
Human Cancer Cell Lines ◽  
Aerial Parts ◽  
Ic50 Values ◽  
Hct 116 ◽  
Relationship Of ◽  
First Time

To obtain diterpene glycosides from an aqueous extract of the aerial parts of Isodon henryi and further investigate their cytotoxicities, in this study, a total of seven compounds were isolated, including six ent-kaurane diterpene glycosides (1–6) and one diterpene aglycon (7). Among the seven ent-kaurane diterpenes obtained, four were novel compounds, including ent-7,20-epoxy- kaur-16-en-1α,6β,7β,15β-tetrahydroxyl-11-O-β-d-glucopyranoside (1), ent-7,20-epoxy-kaur-16-en- 6β,7β,14β,15β-tetrahydroxyl-1-O-β-d-glucopyranoside (2), ent-7,20-epoxy-kaur-16-en-6β,7β,15β- trihydroxyl-1-O-β-d-glucopyranoside (3), and ent-7,20-epoxy-kaur-16-en-7β,11β,14α,15β-tetrahydr- oxyl-6-O-β-d-glucopyranoside (4), and three were isolated from this plant for the first time (5–7). Their structures were elucidated by utilizing spectroscopic methods and electronic circular dichroism analyses. Furthermore, the cytotoxicities of all seven compounds were investigated in four human cancer cell lines, including A2780, BGC-823, HCT-116, and HepG2. The IC50 values of these diterpenes ranged from 0.18 to 2.44 mM in the tested cell lines. In addition, the structure–cytotoxicity relationship of diterpene glycosides was also evaluated to study the effect of glycosylation on the cytotoxicity of diterpene compounds.

Cytotoxicity Assessment of Quassinoids Neosergeolide and Isobrucein B toward Hematopoietic and Solid Malignancies Identifies STAT3 Activation To Be Predictive of Antitumor Response.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1394-1394
Author(s):  
Mitsuteru Hiwatari ◽  
Jingqiu Dai ◽  
Wei Liu ◽  
Yu-Dong Zhou ◽  
Dale G. Nagle ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cytotoxic Activity ◽  
Cell Line ◽  
Cell Lines ◽  
Strong Support ◽  
Luciferase Reporter ◽  
Control Group ◽  
Antitumor Effects ◽  
Protein Levels ◽  
Ic50 Values

Abstract Quassinoids are natural product compounds known to possess tumor cytotoxicity and antimalarial activity. Neosergiolide and isobrucein B are two quassinoids previously isolated from roots and stems of Picrolemma sprucei. In screening studies to identify inhibitors that target STAT3, we discovered neosergeolide and isobrucein B as active compounds. Approximately 5000 plant-derived extracts were screened using a cell line that stably expresses a STAT3-dependent luciferase reporter and NPM-ALK, which constitutively induces STAT3 transcriptional activity. Of 25 total hits, a P. sprucei extract was potent and selective for STAT3 inhibition, and bioassay-guided isolation identified neosergeolide and isobrucein B as the inhibitory compounds. Western blot analysis confirmed that neosergeolide and isobrucein B not only inhibit the tyrosine phosphorylation and activation of STAT3 but also decrease total STAT3 protein levels via a mechanism due in part to enhanced proteasome-mediated degradation. Small-molecule proteasome inhibitors such as MG132 and ALLN reversed the ability of the two quassinoids to decrease STAT3 protein levels; furthermore, simultaneous incubation of various hematopoietic malignancy cell lines with either neosergeolide or isobrucein B and MG132 or ALLN antagonized the cytotoxic activity of the quassinoids. Assessment of neosergiolide and isobrucein B antitumor effects using an XTT assay revealed both compounds to possess potent cytotoxic activity across a broad spectrum of hematopoietic malignancies, with T-leukemias/lymphomas being especially responsive. For example, mycosis fungoides (MF)- and Sezary syndrome (SS)-derived cell lines, as well as non-MF/SS cutaneous T-cell lymphoma (CTCL) lines, were potently inhibited by both quassinoids (neosergiolide IC50 values: MAC-1, 11.6 nM; MAC-2A, 6.9 nM; Hut-78, 6.6 nM; HH, 4.3 nM; MJ, 7.0 nM; isobrucein B IC50 values: MAC-1, 31.9 nM; MAC-2A, 72.3 nM; Hut-78, 23.5 nM; HH; 20.3 nM; MJ, 13.5 nM). Non-hematopoietic cell lines representing various solid tumors also exhibited potent cytotoxic responses to the quassinoids (e.g., gastric carcinoma line AGS [neosergiolide IC50: 16.9 nM; isobrucein B IC50: 114.9 nM]). With rare exceptions, the cytotoxicity of the quassinoids against a specific tumor cell line correlated with STAT3 activation status; for example, breast cancer line MCF7 with inactive STAT3 was resistant to both quassinoids even at the maximum concentration tested (6.25 μM), whereas breast cancer lines MDA-MB-468 and MDA-MB-435s with activated STAT3 were inhibited by both compounds at low concentrations (neosergiolide IC50: MDA-MB-435s, 31.3 nM; MDA-MB-468, 29.9 nM; isobrucein B IC50: MDA-MB-435s, 209.3 nM; MDA-MB-468, 356.8 nM). The in vitro antitumor activity of the two quassinoids could also be demonstrated in vivo. For example, isobrucein B (1.0 mg/kg IP once q 3d x 5 doses) could be safely administered and potently inhibited the growth in SCID mice of the CD30+ primary CTCL MAC-1 cell line; mice at treatment day 16 showed average subcutaneous tumor volumes of 3839 ± 863 (s.e.) mm3 in the vehicle-control group and 913 ± 349 (s.e.) mm3 in the isobrucein B group (P=0.008, t-test). These results provide strong support for STAT3 targeting in antitumor drug discovery and suggest that quassinoids may have utility in such an approach.

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