Inhibitory Activity of Flavonoid Scaffolds on SARS-CoV-2 3CLpro: Insights from the Computational and Experimental Investigations.

The emergence of the COVID-19 situation has become a global issue due to the lack of effective antiviral drugs for treatment. Flavonoids are a class of plant secondary metabolites that have antiviral activity against SARS-CoV-2 through inhibition of the main protease (3CLpro). In this study, 22 flavonoids obtained from natural sources and semisynthetic approaches were investigated for their inhibitory activity against SARS-CoV-2 3CLpro, along with cytotoxicity on Vero cells. The protein-ligand interactions were examined using molecular dynamics simulation. Moreover, QSAR analysis was conducted to clarify the structural effects on bioactivity. Accordingly, the in vitro investigation demonstrated that four flavonoids, namely, tectochrysin (7), 6″,6″-dimethylchromeno-[2″,3″:7,8]-flavone (9), panduratin A (19), and genistein (20), showed higher protease inhibitory activity compared to the standard flavonoid baicalein. Finally, our finding suggests that genistein (20), an isoflavone discovered in Millettia brandisiana, has potential for further development as a SARS-CoV-2 3CLpro inhibitor.

7-Methoxyheptaphylline Enhances TRAIL-Induced Apoptosis of Colorectal Adenocarcinoma Cell via JNK-Mediated DR5 Expression.

A cytokine known as tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has the ability to precisely cause the death of cancer cells, while normal cells are left undisturbed. Recent studies show that certain cancer cells are sensitive to the apoptotic effect of TRAIL. In this study, HT29 colorectal adenocarcinoma cells exposed to TRAIL were treated with heptaphylline and 7-methoxyheptaphylline from Clausena harmandiana in an effort to comprehend the mechanisms involved behind this activity. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test was utilized to determine cell survival, and phase contrast microscopy was used to examine cell morphology. Through using real-time RT-PCR, Western blotting, and RT-PCR, the molecular mechanisms were investigated. According to the findings, whilst hepataphylline caused cytotoxicity in normal colon FHC cells, in comparison to healthy colon FHC cells, 7-methoxyheptaphylline inhibited cancer cells in a concentration-dependent manner. Heptaphylline alone or in conjunction with TRAIL showed no discernible effect on TRAIL-induced HT29 cell death, but 7-methoxyheptaphylline boosted caspase-3 cleavage. The study showed that the c-Jun N-terminal kinase (JNK) pathway was responsible for the 7-methoxyheptaphylline's enhancement of the death receptor 5 (DR5) mRNA, TRAIL receptor, and protein. The results demonstrated that the 7-methoxyheptaphylline of Clausena harmandiana increased the expression of DR5 via the JNK pathway, intensifying TRAIL-induced HT29 cell death.

Multifunctionality of Clausena harmandiana Extract and Its Active Constituents against Alzheimer's Disease.

This study was designed to investigate the effects of the root-bark extract of Clausena harmandiana (CH) and its active constituents (nordentatin and 7-methoxyheptaphylline) on pharmacological activities regarding selected targets associated with AD, namely, its antioxidant activity, inhibition of Aß aggregation, acetylcholinesterase (AChE) activity, and neuroprotective effects. The effect of the CH extract on the cognitive impairment induced by scopolamine was also evaluated in mice. The effects of the CH extract and its active constituents on radical scavenging, Aß aggregation, and AChE activity were investigated with a 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) assay, a thioflavin-T assay, and Ellman's method. The neuroprotective effects of the extract against hydrogen-peroxide and Aß toxicity were evaluated with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. In addition, the effects on cognitive impairment induced by scopolamine in mice were evaluated using Morris-water-maze and modified-Y-maze test models. The results of the present study demonstrate that the root-bark extract of CH shows multimodal actions relevant to the AD pathological cascade, including antioxidant effects, the inhibition of Aß aggregation, the inhibition of AChE function, and neuroprotection against oxidative stress and Aß toxicity. The extracts could improve both the short- and long-term memory deficits induced by scopolamine in mice.

Nordentatin Inhibits Neuroblastoma Cell Proliferation and Migration through Regulation of GSK-3 Pathway.

Cancer is caused by abnormal cell changes leading to uncontrolled cell growth. The specific characteristics of cancer cells, including the loss of apoptotic control and the ability to migrate into and invade the surrounding tissue, result in cancer cell metastasis to other parts of the body. Therefore, the inhibition of the proliferation, migration, and invasion of cancer cells are the principal goals in the treatment of cancer. This study aimed to investigate the inhibitory activity of nordentatin, a coumarin derivative isolated from Clausena harmandiana, regarding the proliferation and migration of human neuroblastoma cells (SH-SY5Y). Nordentatin at a concentration of 100 µM showed cell cytotoxicity toward SH-SY5Y that was significantly different from that of the control group (p < 0.01) at 24, 48, and 72 h. Moreover, nordentatin inhibited SH-SY5Y proliferation by inhibiting the antiapoptotic protein Mcl-1, leading to the cleavage of caspase-3 and resulting in the inhibition of a migratory protein, MMP-9, through the GSK-3 pathway (compared with cells treated with a GSK inhibitor). These results suggest that nordentatin inhibited the proliferation and migration of neuroblastoma cells through the GSK-3 pathway.

A new sesquiterpenoid juvenile hormone III from the stems of Cananga latifolia.

A new juvenile hormone III, canangalia I (1), along with six known juvenile hormone III analogues (2-7), was isolated from the methanolic extract of Cananga latifolia stems. All structures were elucidated using spectroscopic data and compared with data from previous literature. Canangalia I (1) was found to be cytotoxic against human cervical adenocarcinoma (HeLa) cells with an IC50 value of 35.00 ± 2.15 µg/ml after 72 h, but was not toxic to Vero cells.

Histone Deacetylase Inhibitory Activity and Antiproliferative Potential of New [6]-Shogaol Derivatives.

Twenty newly synthesized derivatives of [6]-shogaol (4) were tested for inhibitory activity against histone deacetylases. All derivatives showed moderate to good histone deacetylase inhibition at 100 µM with a slightly lower potency than the lead compound. Most potent inhibitors among the derivatives were the pyrazole products, 5j and 5k, and the Michael adduct with pyridine 4c and benzothiazole 4d, with IC50 values of 51, 65, 61 and 60 µM, respectively. They were further evaluated for isoform selectivity via a molecular docking study. Compound 4d showed the best selectivity towards HDAC3, whereas compound 5k showed the best selectivity towards HDAC2. The potential derivatives were tested on five cancer cell lines, including human cervical cancer (HeLa), human colon cancer (HCT116), human breast adenocarcinoma cancer (MCF-7), and cholangiocarcinoma (KKU100 and KKU-M213B) cells with MTT-based assay. The most active histone deacetylase inhibitor 5j exhibited the best antiproliferative activity against HeLa, HCT116, and MCF-7, with IC50 values of 8.09, 9.65 and 11.57 µM, respectively, and a selective binding to HDAC1 based on molecular docking experiments. The results suggest that these compounds can be putative candidates for the development of anticancer drugs via inhibiting HDACs.

Acridone Derivatives from Atalantia monophyla Inhibited Cancer Cell Proliferation through ERK Pathway.

The present study aimed to investigate the effect of acridone alkaloids on cancer cell lines and elucidate the underlying molecular mechanisms. The ten acridone alkaloids from Atalantia monophyla were screened for cytotoxicity against LNCaP cell lines by a WST-8 assay. Then, the most potential acridone, buxifoliadine E, was evaluated on four types of cancer cells, namely prostate cancer (LNCaP), neuroblastoma (SH SY5Y), hepatoblastoma (HepG2), and colorectal cancer (HT29). The results showed that buxifoliadine E was able to significantly inhibit the proliferation of all four types of cancer cells, having the most potent cytotoxicity against the HepG2 cell line. Western blotting analysis was performed to assess the expression of signaling proteins in the cancer cells. In HepG2 cells, buxifoliadine E induced changes in the levels of Bid as well as cleaved caspase-3 and Bax through MAPKs, including Erk and p38. Moreover, the binding interaction between buxifoliadine E and Erk was investigated by using the Autodock 4.2.6 and Discovery Studio programs. The result showed that buxifoliadine E bound at the ATP-binding site, located at the interface between the N- and C-terminal lobes of Erk2. The results of this study indicate that buxifoliadine E suppressed cancer cell proliferation by inhibiting the Erk pathway.

Candidone Inhibits Migration and Invasion, and Induces Apoptosis in HepG2 Cells.

The aim of the study was to investigate the inhibitory activity of candidone, the active constituent of Derris (D.) indica, on the proliferation, migration, and invasiveness of human hepatoblastoma (HepG2) cells. Cancer cell death was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and apoptosis-associated morphological changes were observed by phase contrast microscopy. Additionally, Western blotting was used to study protein expression following treatment with candidone, and transwell migration and invasion assays were used for observing cancer cell migration and invasiveness, respectively. The results suggest that candidone possesses potent inhibitory activity against HepG2 cells (concentration, 100 µM; 24 h treatment). Cancer cells treated with candidone exhibited apoptosis-associated changes, including detachment, cell shrinkage and death. Furthermore, candidone was shown to promote cell death by activating caspase-3 and -9, and decreasing the expression of antiapoptotic proteins, including p65, induced myeloid leukemia cell differentiation protein Mcl-1, B-cell lymphoma 2 (Bcl2), Bcl2-associated agonist of cell death and survivin. Moreover, candidone inhibited the migration and invasion abilities of HepG2 cells and decreased the levels of proteins associated with these processes, including phospho-p38 and active matrix metallopeptidase 9. Collectively, the results of the present study indicate that candidone is able to inhibit the proliferation, migration and invasive potential of HepG2 cells.

Influence of side-chain changes on histone deacetylase inhibitory and cytotoxicity activities of curcuminoid derivatives.

Using curcuminoids as lead compounds, fifty-nine curcuminoid derivatives with different side chains at the phenolic moiety were synthesized. All compounds were investigated for their histone deacetylase (HDAC) inhibitory activities. The potent pan-HDAC inhibitors were further tested against three human cancer cell lines including Hela, HCT116 and MCF-7 with MTT-based assay. The bisethylamide 4z and the mono-sec-butyl derivative 5j manifested good antiproliferative activities against HCT116 cancer cells with the IC50 values as 14.60 ± 1.19 µg/mL and 7.33 ± 0.98 µg/mL, respectively. Molecular docking study of both compounds with Class I HDACs revealed that the compounds might bind tightly to the binding pocket of HDAC2. These findings suggested that these compounds can be putative candidates for the development of anticancer drugs via inhibiting HDACs.

Analysis of xanthyletin and secondary metabolites from Pseudomonas stutzeri ST1302 and Klebsiella pneumoniae ST2501 against Pythium insidiosum.

BACKGROUND: Pythium insidiosum is a member of the oomycetes class of aquatic fungus-like microorganisms. It can infect humans and animals through skin wounds and the eyes, causing pythiosis, an infectious disease with high morbidity and mortality rates. Antifungal agents are ineffective as pythiosis treatments because ergosterol, the target site of most antifungal agents, is not found in the P. insidiosum cytoplasmic membrane. The best choice for treatment is surgical removal of the infected organ. While natural plant products or secretory substances from bacterial flora have exhibited in vitro anti-P. insidiosum activity, their mechanism of action remains unknown. Therefore, this study hypothesized that the mechanism of action could be related to changes in P. insidiosum biochemical composition (such as lipid, carbohydrate, protein or nucleic acid) following exposure to the inhibitory substances. The biochemical composition of P. insidiosum was investigated by Synchrotron radiation-based Fourier-transform infrared (FTIR) microspectroscopy. RESULTS: Fraction No.6 from the crude extract of P. stutzeri ST1302, fraction No.1 from the crude extract of K. pneumoniae ST2501 and xanthyletin were used as anti-P. insidiosum substances, with MFCs at 3.125, 1.57-1.91, 0.003 mg/ml, respectively. The synchrotron FTIR results show that the deconvoluted peak distributions in the amide I, amide II, and mixed regions were significantly different between the treatment and control groups. CONCLUSIONS: Xanthyletin and the secondary metabolites from P. stutzeri ST1302 and K. pneumoniae ST2501 exerted anti-P. insidiosum activity that clearly changed the proteins in P. insidiosum. Further study, including proteomics analysis and in vivo susceptibility testing, should be undertaken to develop a better understanding of the mechanism of anti-P. insidiosum activity.

Styrenes from the Seeds of Atalantia monophylla.

Four new dimeric styrenes, 1-4, were isolated from an EtOAc crude extract of the seeds of Atalantia monophylla. The biosynthetic pathway of 1 is proposed to involve a [2 + 2] cycloaddition, while 2-4 may be generated via a polar mechanism with a carbocation as the key intermediate. The structures of 1-4 were defined from spectroscopic analysis; experimental and calculated ECD spectra were used to characterize their absolute configurations. When tested against two different cancer cell lines, 1-4 were not determined to be cytotoxic (IC50 > 10 µM).

Benzoyltyramine Alkaloids Atalantums A-G from the Peels of Atalantia monophylla and Their Cytotoxicity against Cholangiocarcinoma Cell Lines.

Seven new benzoyltyramines, atalantums A-G (1-7), and five known compounds were isolated from the peels of Atalantia monophylla. All compounds were examined for cytotoxicity against the cholangiocarcinoma cell lines KKU-M214, KKU-M213, and KKU-M156. Compound 5 exhibited the strongest cytotoxicity against KKU-M156 cells, with an IC50 value of 1.97 ± 0.73 µM, an approximately 4.7-fold higher activity than that of the ellipticine standard. Compound 1 displayed strong cytotoxicity against KKU-M214 cells, with an IC50 value of 3.06 ± 0.51 µM, nearly equal to that of the 5-fluorouracil standard. In the case of the KKU-M213 cell line, compounds 2, 4, and 11 exhibited stronger cytotoxicity than the ellipticine standard, with IC50 values of 2.36 ± 0.20, 5.63 ± 0.22, and 2.71 ± 0.23 µM, respectively. Compounds 1, 5, and 7 displayed cytotoxicity against KKU-M214 cells, with IC50 values of 3.06 ± 0.51, 8.44 ± 0.47, and 7.37 ± 1.29 µM, respectively.

Cytotoxic flavonoids from the fruits of Derris indica.

Chemical investigation of the ethyl acetate extract from the fruits of Derris indica has led to the isolation of a new furanoflavonoid derivative, 4'-hydroxypinnatin (1), and five known compounds. Pinnatin (2) showed strong cytotoxicity against cholangiocarcinoma (KKU-100) and human hepatoma (HepG2) cell lines with IC50 values of 6.0 ± 2.7 and 9.0 ± 4.1 µg/ml, respectively, and showed maximal cell killing effect of about 88-90%. Flavone 5 exhibited the most cytotoxicity against KKU-100 but it showed moderate efficacy (Emax = 50.7%).

Terpenoids from the root bark of Pterolobium macropterum.

Five new compounds, including pteroloterins A-C (1, 3, and 4), 1ß-acetoxytaepeenin C (2), and 8aα-hydroxycadinenal (5), and 11 known compounds were isolated from the root bark of Pterolobium macropterum. All compounds were evaluated for cytotoxicity against the cholangiocarcinoma cell lines. Compound 9 showed weak cytotoxicity against the KKU-M139 cell line with an IC50 value of 23.24 ± 0.18 µM and showed no activity against normal cells.

Cytotoxic coumarins from Toddalia asiatica.

Three new coumarins and 13 known compounds were isolated from the stem bark of Toddalia asiatica. Compounds 1, 3, 8, and 9 showed cytotoxicity against the NCI-H187 cell line with IC50 values ranging from 6 to 9 µg/mL. Compounds 4 and 9 exhibited cytotoxicity against the MCF-7 cell line with IC50 values of 3.17 and 9.79 µg/mL, respectively. Compound 9 also displayed cytotoxic activity against KB cells with an IC50 value of 8.63 µg/mL. In addition, compound 14 showed antimalarial activity against Plasmodium falciparum with an IC50 value of 3.66 µg/mL. Compounds 5, 9, and 16 exhibited antituberculosis activity against Mycobacterium tuberculosis with MIC values of 50, 50, and 25 µg/mL, respectively.

Evaluation and molecular docking study of two flavonoids from Oroxylum indicum (L.) Kurz and their semi-synthetic derivatives as histone deacetylase inhibitors.

Chrysin (5,7-dihydroxyflavone, 6) and galangin 3-methyl ether (5,7-dihydroxy-3-methoxy flavone, 7) were obtained from the leaves of Oroxylum indicum (L.) Kurz in 4% and 6% yields, respectively. Both compounds could act as pan-histone deacetylase (HDAC) inhibitors. Structural modification of these lead compounds provided thirty-eight derivatives which were further tested as HDAC inhibitors. Compounds 6b, 6c, and 6q were the most potent derivatives with the IC50 values of 97.29 ± 0.63 µM, 91.71 ± 0.27 µM, and 96.87 ± 0.45 µM, respectively. Molecular docking study indicated the selectivity of these three compounds toward HDAC8 and the test against HDAC8 showed IC50 values in the same micromolar range. All three compounds were further evaluated for the anti-proliferative activity against HeLa and A549 cell lines. Compound 6q exhibited the best activity against HeLa cell line with the IC50 value of 13.91 ± 0.34 µM. Moreover, 6q was able to increase the acetylation level of histone H3. These promising HDAC inhibitors deserve investigation as chemotherapeutic agents for treating cancer.

Five new quinoline alkaloids from Sauropus hirsutus Beille and their cytotoxicity.

Chemical investigation of the whole plant of Sauropus hirsutus Beille led to the isolation of eight quinolines and two known flavonoids. Furthermore, five quinolines were new, two were reported in plant for the first time and one was known. Cytotoxicity evaluation against cholangiocarcinoma, KKU-M156, showed that the most active compound was 4-hydroxy-6-methoxy-7,8-methylenedioxyquinaldine (IC50 20.54 ± 6.82 µM) which was a little more active than the cisplatin standard (IC50 24.39 ± 1.14 µM).

A rare isoflavone-quinone and a new flavanone from the roots of Dalbergia stipulacea Roxb.

Two previously undescribed compounds, namely dalpulapans F and G (1 and 2), along with 11 known compounds were isolated from the MeOH crude extract of the roots of Dalbergia stipulacea. Dalpulapan F was found as a rare isoflavone-quinone derivative. Their structures and absolute configurations were supported by extensive spectroscopic data analysis, including 1 D and 2 D NMR, HRESIMS data, specific rotation data, and comparison of the experimental and calculated ECD data. Cytotoxicity evaluation of the isolated compounds against HepG2 and KKU-M156 cell lines revealed that isoflavonoid 9 and rotenoid 13 exhibited the most activity against the two cell lines.

Neuroprotective and anticancer effects of 7­Methoxyheptaphylline via the TAK1 pathway.

7­Methoxyheptaphylline (7­MH) is a carbazole extracted from Clausena harmandiana, a medicinal plant that is used to treat headaches and stomachaches. The aim of the present study was to examine the neuroprotective effects and anticancer activity of 7­MH. Cell death was assessed using an MTT assay and flow cytometry. The expression of apoptosis­related proteins was determined by western blot analysis. An animal model was used to test anti­metastasis. The interactions between 7­MH and the molecular target were observed using molecular docking. The results revealed that 7­MH provided protection against hydrogen peroxide (H2O2)­induced neuronal cell death. In cancer cells, 7­MH induced SH­SY5Y, 4T1, HT29, HepG2, and LNCaP cell death. 7­MH inhibited metastasis of HT29 cells in vitro and 4T1­Luc cells in vitro and in vivo. 7­MH inhibited proteins, including P­glycogen synthase kinase (GSK)­3, and cleaved caspase­3, but it activated anti­apoptotic proteins in H2O2­induced SH­SY5Y cell death. By contrast, 7­MH activated the cleaving of caspase­3 and GSK­3, but it suppressed anti­apoptotic proteins in SH­SY5Y cells. 7­MH reduced the levels of NF­κB and STAT3 in 4T1 cells; phospho­p65, Erk, and MAPK13 in LNCaP cells; and phospho­Erk and matrix metalloproteinase­9 in HT29 cells. Molecular docking analysis showed that 7­MH targets TAK1 kinase. The present study indicated that 7­MH induced apoptosis of cancer cells and provided protection against H2O2­induced neuron cell death via TAK1 kinase.

Anti-inflammatory effects of Derris scandens extract on narrowband-ultraviolet B exposed HaCaT human keratinocytes.

Narrowband-ultraviolet B (NB-UVB) has been used to treat skin diseases such as psoriasis. Chronic use of NB-UVB might cause skin inflammation and lead to skin cancer. In Thailand, Derris Scandens (Roxb.) Benth. is used as an alternative medicine to nonsteroidal anti-inflammatory drugs (NSAIDs) for low back pain and osteoarthritis. Therefore, this study aimed to evaluate the potential anti-inflammatory effect of Derris scandens extract (DSE) on pre- and post exposed NB-UVB human keratinocytes (HaCaT). The results indicated that DSE could not protect HaCaT from cell morphology changes or DNA fragmentation and could not recover cell proliferation ability from the NB-UVB effects. DSE treatment reduced the expression of genes related to inflammation, collagen degradation, and carcinogenesis, such as IL-1α, IL-1ß, IL-6, iNOS, COX-2, MMP-1, MMP-9, and Bax. These results indicated the potential use of DSE as a topical preparation against NB-UVB-induced inflammation, anti-aging, and prevention of skin cancer from phototherapy.