Two new stilbenoids from Pleione bulbocodioides

Two new stilbenoids, 9-(4′-hydroxy-3′-methoxyphenyl)-10-(hydroxymethyl)-11-methoxy-5,6,9,10-tetrahydrophenanthro[2,3-b]furan-3-ol (1) and 2-(4″-hydroxybenzyl)-3-(3′-hydroxyphenethyl)-5-methoxy-cyclohexa-2,5-diene-1,4-dione (2), together with the three known stilbenoids were isolated from the tubers of Pleione bulbocodioides (Franch.) Rolfe. Their structures were elucidated by spectroscopic methods.     

Chemical constituents inAloe barbadensis

Two compounds were newly isolated from the leaves ofAloe barbadensis Mill. Their structures were identified as 3,4-dihydro-3,9-dihydroxy-8-methoxy-3-methyl-1(2H)-anthracenone(1) and 10-β-D-glucopyranosyl-1,8,10-trihydroxy-3-(hydroxymethyl)-(R)-9(10)-anthracenone(2) by chemical and spectral evidences.     

New glycosides from <Emphasis Type="Italic">Dracocephalum tanguticum</Emphasis> maxim

Four new glycosides, luteolin-7-methoxy-3′-O-(3″-O-acetyl)-β-D-gluco pyranuronic acid-6″-methyl ester (1), benzyl-6-[(2E)-2-butenoate]-β-D-glucopyranoside (2), 2-methoxy-4-(2-propen-1-yl)penyl-6-acetate-β-D-glucopyranoside (3), and 2-methoxy-4-(2-propen-1-yl)penyl-6-[(2E)-2-butenoate]-β-D-glucopyranoside (4), along with benzyl-β-D-glucopyranoside (5), 2-methoxy-4-(2-propen-1-yl)penyl-β-D-glucopyranoside (6), and pectolarigenin (7), were isolated from the whole plant of Dracocephalum tanguticum Maxim. The structures of 1-4 were elucidated by detailed spectroscopic analyses, including HR-ESI-MS and 2D NMR spectroscopic data. The inhibitory effects against nitric oxide production in LPS-stimulated RAW264.7 cells of all seven compounds were also evaluated.     

Studies on synthesis and heterocyclisation reactions of michael products and formation of new 1,4-thiazine quinoxaline derivatives

Synthesis of α-piperidino and α-morphelino styryl’quinoxalinone2f, 2g respectively by facile one step method is reported. The Michael adducts (3a-d) obtained by the interaction of 2-styryl-2 (1H) quinoxalinone (2) and ethylacetoacetate have been treated with resorcinol and hydroxylamine separatly. With resorcinol the chromones (4) are obtained whereas with hydroxylamine isoxazolones (6) are the products. Michael addition of acetylacetone to2 leads to 3-[1′-aryl-2′-(2′-hydroxy-3′-quinoxalinyl)ethyl]-2,4-pentanediones (5) which undergo cyclisation with hydroxylamine to give isoxazoles (7). Addition of thiophenol and thioglycolic acid to2 gives3-α-[β-(phenyl)-β-(plenylthio)]ethyl-2(1H)-quinoxalinone (8) and 3-α-[β-phenyl)-β-(hydroxycarbonylmethylthio)]-ethyl-2(1H)-quinox-alinone (9) respectively. 2-Bromomethyl-2(1H)-quinoxalinone (1b) reacts with thioglycolic acid to gives S-[2 (1H)-oxoquinoxalin-3-yl-methyl]mercaptoacetic acid (10) which on cyclisation with acetic anhydride/pyridine affords 1,2,5,6-tetrahydro[1,4]thiazino[4,3-a] quinoxaline-1,6-dione (11).     

Synthesis and antitumor evaluation ofcis-(1,2-diaminoethane) dichloroplatinum (II) complexes linked to 5- and 6-methyleneuracil and-uridine analogues

The search for platinum (II)-based compounds with improved therapeutic properties was prompted to design and synthesize a new family of water-soluble, third generation cis-diaminedichloroplatinum (II) complexes linked to uracil and uridine. Six heretofore unreported uracil and uridine-platinum (II) complexes are; [N-(uracil-5-yl-methyl)ethane-1,2-di-amine]dichloroplatinum (II) (3a), [N-(uracil-6-yl-methyl)ethane-1,2-diamine] dichloroplatinum (II) (3b), {[N-(2′,3′,5′-tri-O-acetyl)uridine-5-yl-methyl] ethane-1,2-diamine}dichloroplatinum (II) (6a), {[N-(2′,3′,5′-tri-O-acetyl) uridine-6-yl-methyl]ethane-1,2-diamine}dichloroplatinum (II) (6b), [N-(uridine-5-yl-methyl)ethane-1,2-diamine]dichloroplatinum (II) (7a), [N-(uridine-6-yl- methyl)ethane-1,2-diamine]dichloroplatinum (II) (7b). These analogues were prepared from the key starting materials, 5-chloromethyluracil (1a) and 6-chloromethyluracil (1b) which were reacted with ethylenediamine to afford the respective 5-[(2-aminoethyl)amino] methyluracil (2a) and 6-[(2-aminoethyl)amino]methyluracil (2b). The cis-platin complexes3a and3b were obtained through the reaction of the respective2a and2b with potassium tetrachloroplatiate (II). The heterocyclic nucleic acid bases1a and1b were efficiently introduced on the β-D-ribose ring via a Vorbruggen-type nucleoside coupling procedure with hexamethyldisilazane, trimethylchlorosilane and stannic chloride under anhydrous acetonitrile to yield the stereospecific β-anomeric 5-chloromethyl-2′,3′,5′-tri-O-acetyluridine (4a) and 6-chloromethyl-2′,3′,5′-tri-O-acetyluridine (4b), respectively. The nucleosides4a and4b were coupled with ethylenediamine to provide the respective 5-[(amino-ethyl)amino]methyl-2′,3′,5′-tri-O-acetyluridine (5a) and 6-[(aminoethyl)amino] methyl-2′,3′,5′-tri-O-acetyluridine (5b). The diamino-uridines5a and5b were reacted with potassium tetrachloroplatinate (II) to give the novel nucleoside complexes,6a and6b, respectively which were deacetylated into the free nucleosides,7a and7b by the treatment with CH₃ONa. The cytotoxic activities were evaluated against three cell lines (FM-3A, P-388 and J-82) and none of the synthesized compounds showed any significant activity.     

Synthesis and biological activity studies of new hybrid molecules containing tryptamine moiety

The synthesis of N′-(4-substitutedphenylsulfonyl)-2-{4-[2-(1H-indol-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}acetohydrazides (3a–c), 2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-aryl methylidene acetohydrazides (4a–f) and 4-[2-(1H-indol-3-yl)ethyl]-5-(4-substitutedbenzyl)-2-[(5-sulfanyl-1,3,4-oxadiazol-2-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-ones (5a, b) was performed starting from the corresponding acid hydrazides (2a, b) which was reported earlier. The treatment of 1,3,4-oxadiazole derivatives (5a, b) with hydrazine hydrate produced 4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl derivatives (6a, b). Then, compound 6b was converted to the corresponding Schiff base (7) by the treatment with anisaldehyde. The synthesis of 5-(4-chlorobenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (8) and 5-(4-methylbenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (10) was carried out by the reaction of acid hydrazides (2a, b) with aryl iso(thio)cyanates either via the formation of the intermediates (9a, b) (for 10) or direct cyclization (for 8). 1,3-Oxa(thia)zol-2(3H)-ylidene]acetohydrazide derivatives (11a, b) were obtained by the reaction of 9a, b with 4-chlorophenacyl bromide. All newly synthesized compounds were screened for their antimicrobial activities and some of which was found to be active against the test microorganisms.     

Aromatic compounds from the halotolerant fungal strain of <Emphasis Type="Italic">Wallemia sebi</Emphasis> PXP-89 in a hypersaline medium

A new cyclopentanopyridine alkaloid, 3-hydroxy-5-methyl-5,6-dihydro-7H-cyclopenta[b]pyridin-7-one (1), together with 11 known aromatic compounds were isolated from the secondary metabolites of the halotolerant fungal strain Wallemia sebi PXP-89 in 10% NaCl. Their structures including the absolute configurations of (2S,3S)-1-(4-hydroxyphenyl)butane-2,3-diol (2), (2R,3S)-1-(4-hydroxyphenyl)butane-2,3-diol (3), and (S)-3-hydroxy-4-(4-hydroxyphenyl)-2-one (4) were elucidated by spectroscopic analysis and a modified Mosher’s method. Compound 1 exhibited antimicrobial activity against Enterobacter aerogenes with a MIC of 76.7 μM. The absolute configurations of compounds 2–4 were determined for the first time.     

Synthesis of 1,4-dihydropyridine carboxylic acids (III)

2,6-Dimethyl-4-(3′-nitrophenyl)-3-methoxylaminocarbonyl-1,4-dihydropyridine-5-carboxylic acid methylester,3b reacted with 2-cyanoethanol or benzylalcohol to give the corresponding cyanoethylurethane compound6c in 40.6% yield and benzylurethane compound6d in 32% yield. The cyanoethylurethane6c was hydrolized in ethanolic NaOH to give 2,6-dimethyl-4-(3′-nitrophenyl)-1,4-dihydropyridine-3-amino-5-carboxylic acid 5-methyl ester. HCl8 in 64.8% yield. Another acid hydrolysis of benzylurethane6d gave 2,6-dimethyl-4-(3′-nitrophenyl)-1,4-dihydropyridine-3-amino-5-carboxylic acid 5-methylester. HBr11 in 54.7% yield.     

Chemical constituents of <Emphasis Type="Italic">Melandrium firmum</Emphasis> Rohrbach and their anti-inflammatory activity

In our ongoing search for anti-inflammatory agents originating from Korean medicinal plants, we found that the hexane and BuOH fractions of the MeOH extract from the whole plants of Melandrium firmum Rohrbach inhibited 5-lipoxygenase (5-LOX) activity. By activity-guided fractionation, eleven compounds, α-spinaterol (1), ursolic acid (2), ergosterol peroxide (3), α-spinaterol glucoside (4), 2-methoxy-9-β-D-ribofuranosyl purine (5), aristeromycin (6), ecdysteron (7), polypodoaurein (8), (-)-bornesitol (9), mannitol (10) and cytisoside (11) were isolated from the hexane and BuOH fractions using column chromatography. Compounds 2, 5, 6, 8, 9, 10 and 11 were isolated for the first time from this plant. Compounds 1, 3, 4 and 7 inhibited 5-LOX activity with IC₅₀ values of 21.04 μM, 42.30 μM, 32.82 μM, and 17.18 μM, respectively. Ming Shan Zheng and Nam Kyung Hwang contributed equally to this work.     

Stilbene and dihydrophenanthrene derivatives from <Emphasis Type="Italic">Pholidota chinensis</Emphasis> and their nitric oxide inhibitory and radical-scavenging activities

Two new stilbene derivatives, (E)-2′,3,3′-trihydroxy-5-methoxystilbene (1, Pholidotol C) and (Z)-3,3′-hydroxy-5-methoxystilbene (2, Pholidotol D), were isolated from the air-dried whole plant of Pholidota chinensis Lindl., together with eight known dihydrophenanthrene derivatives, lusianthridin (3), cannabidihydrophenanthrene (4), coelonin (5), hircinol (6), erianthridin (7), 4,5-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (8), eulophiol (9), and 2,4,7-trihydroxy-9,10-dihydrophenanthrene (10), and a benzoxepin derivative bulbophylol B (11). Their inhibitory effects on nitric oxide (NO) production activity and 1,1-diphenyl-2-picrylhydrazil radical-scavenging activity were examined. Among these compounds, 11 exhibited the most potent activity toward NO production inhibition activity and radical-scavenging activity; moreover, 11 reduced inducible nitric oxide synthase mRNA expression.     

A new prenylated dihydrochalcone from the leaves of <Emphasis Type="Italic">Artocarpus lowii</Emphasis>

A new prenylated dihydrochalcone, 2′,4′-dihydroxy-4-methoxy-3′-prenyldihydrochalcone (1), along with two known compounds, 2′,4′,4-trihydroxy-3′-prenylchalcone (2) and 2′,4-dihydroxy-3′,4′-(2,2-dimethylchromene)chalcone (3) were isolated from the leaves of Artocarpus lowii. The structures of 1–3 were elucidated by spectroscopic methods and by comparison with data reported in the literature. Compounds 1–3 showed strong free radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) measured by electron spin resonance (ESR) spectrometry.     

Two new isoflavanones from Erythrina costaricensis

Two new isoflavanones, 5,3′-dihydroxy-4′-methoxy-5′-(3-methyl-1,3-butadienyl)-2″,2″-dimethylpyrano[5,6:6,7]isoflavanone (1) and 5,3′-dihydroxy-5′-(3-hydroxy-3-methyl-1-butenyl)-4′-methoxy-2″,2″-dimethylpyrano[5,6:6,7]isoflavanone (2), together with two known isoflavonoids, cristacarpin, and euchrenone b₁₀, were isolated from the stems of Erythrina costaricensis. Their structures were established on the basis of spectroscopic evidence. These new compounds are rare isoflavanones, possessing both a 2,2-dimethylpyran substituent and a prenyl analog. The antibacterial activities of 1 and 2 against the methicillin-resistant Staphylococcus aureus were examined.     

DNA binding,antiviral activities and cytotoxicity of new furochromone and benzofuran derivatives

Bromination of visnagin (1) afforded 9-bromovisnagin (2) which on its alkaline hydrolysis afforded the 3-acetyl benzofuran derivative (3). The condensation of (3) with hydrazine hydrate, phenylhydrazine and/or hydroxylamine hydrochloride afforded the corresponding pyrazole derivatives (4a, b) and isoxazole derivative (4c). On the other hand, when compound 3 was condensed with some aromatic aldehydes, this yielded corresponding α, β-unsaturated keto derivatives (5a–e). Furthermore, when 1 was subjected to chlorosulfonation, the visnaginsulfonylchloride derivative 6 was afforded, which on amidation using morpholine, a sulonamido derivative (7) was obtained. Alkaline hydrolysis of the latter compound yielded 7-N-morpholinosulsamidobenzofuran (8) which was condensed with some aromatic aldehydes to yield the corresponding chalcone compounds (9a–e). Demethylation of visnagin afforded norvisnagin (10). The reaction of 10 with ethylbromoacetate in dry acetone yielded the ester benzopyran derivative (11) which reacted with hydrazine hydrate to afford the corresponding hydrazide derivative (12) and this was condensed with 3,4,5-trimethoxybenzaldehyde to give the corresponding hydrazone (13). A thaizolidinone derivative (14) was obtained by condensation of (13) with thioglycolic acid. Chloromethylation of norvisnagin afforded a 4-chloromethyl derivative (15) which reacted with different primary and secondary amines to yield the corresponding ethylamino derivative (16a, b). Moreover, mannich bases (16a, b) and (17a–c) were obtained by reacting norvisnagin with different primary and secondary amines in the presence of formalin but benzoylation of (16a, b) and (17a–c) afforded 4-oxybenzoyl derivative (18a–e). The prepared compounds were tested for their interaction with DNA; bromovisnagin 2 showed the highest affinity and compounds 6, 15, 8a, > 14, > 16b, 17a, and 16a showed moderate activity in decreasing potency. Moreover, compound 2 also was the most active as antiviral agent toward HS-I virus and compounds 6, 7, 15, 14, 16a, and 18a were found to be moderately active. CD₅₀ of the active compounds were also measured.     

Synthesis of certain mercapto-and aminopyrimidine derivatives as potential antimicrobial agents

Reaction of ethyl 4-chloro-2-phenylpyrimidine-4-carboxylate (4) with 5-chloro-2-methylthiophenol or 3-aryl-4-phenyl-1,2,4-triazole-5-thiol yielded the corresponding thioethers (5) and (8a, b), respectively. Careful alkaline hydrolysis of (5) yielded the corresponding carboxylic acid (6). Reaction of (4) withp-aminoacetophenone yielded compound (10) which was reacted with certain aromatic aldehydes to afford the α, β-unsaturated ketones (11a–d). Condensation of (11a–d) with malononitrile or phenylhydrazine yielded the 2-amino-3-cyanopyridines (12a–f) or the 2-pyrazolines (13a, b), respectively. Seven representative compounds were tested for theirin vitro antimicrobial activity against some pathogenic micro-organisms, some of them were proved to be active.     

Chalcones isolated from <Emphasis Type="Italic">Angelica keiskei</Emphasis> and their inhibition of IL-6 production in TNF-α-stimulated MG-63 cell

Six chalcone compounds, 2′,4′,4-trihydroxy-3′-[2-hydroxy-7-methyl-3-methylene-6-octaenyl]chalcone (1), 2′,4′,4-trihydroxy-3′-geranylchalcone (2), 2′,4′,4-trihydroxy-3′-[6-hydroxy-3,7-dimethyl-2,7-octadienyl]chalcone (3), 2′,4-dihydroxy-4′-methoxy-3′-[2-hydroperoxy-3-methyl-3-butenyl]chalcone (4), 2′,4-dihydroxy-4′-methoxy-3′-geranylchalcone (5), and 2′,4-dihydroxy-4′-methoxy-3′-[3-methyl-3-butenyl]chalcone (6) were isolated from the leaves of Angelica keiskei K (Umbelliferae). The structure of each isolated compound was determined using spectroscopic methods. Among the isolates, compounds 1–3 appeared to have potent inhibitory activity of IL-6 production in TNF-α-stimulated MG-63 cell, while compounds 4–6 did not. The distinct structural difference between compounds 1–3 and 4–6 was the presence of C-4′ hydroxyl group in the chalcone moiety. Our results imply that the inhibitory activity of IL-6 production in TNF-α-stimulated MG-63 cell may be affected by the presence of C-4′ hydroxyl group in the chalcone moiety.     

Four new glucosides from the aerial parts of Mediasia macrophylla

As part of our chemical studies on the medical plants in Uzbekistan aimed at searching for new drug leads, we have examined the aerial parts of Mediasia macrophylla. This has resulted in the isolation of four new glucosides, together with 30 known compounds. The structures of new compounds were elucidated as (1′S)-(4-hydroxyphenyl) ethane-1′,2′-diol 2′-O-β-glucopyranoside (1), 3-(4′-methoxyphenyl)-propanol 1-O-β-glucopyranoside (2), 2-methoxy-3-hydroxy-5-(E)-propenyl-phenol 1-O-β-glucopyranoside (3), 1-O-angeloyl-β-glucopyranose (4), on the basis of spectral analysis.     

Cytotoxic 10-(indol-3-yl)-[13]cytochalasans from the fungus <Emphasis Type="Italic">Chaetomium elatum</Emphasis> ChE01

Nine 10-(indol-3-yl)-[13]cytochalasans such as a new chaetoglobosin V (1); two new natural products, prochaetoglobosin III (2) and prochaetoglobosin III_ed (3); six known chaetoglobosins B-D (4–6), F (7), and G (8) and isochaetoglobosin D (9) in addition to two known sterols, 24(R)-5α,8α-epidioxyergosta-6–22-diene-3β-ol (10) and ergosterol (11), were isolated from the fungus Chaetomium elatum ChE01. The structures of these compounds were elucidated by spectroscopic methods. Compounds 1–9 showed cytotoxicity against the human breast cancer (IC₅₀ 2.54–21.29 μM) and cholangiocarcinoma cell lines (IC₅₀ 3.41–86.95 μM).     

The synthesis and antimicrobial activities of some 1,4-naphthoquinones (II)

In order to evaluate the antimicrobial effect of 2,3-disubstituted-1,4-naphthoquinone derivatives we newly synthesized several 2-chloro and 2-bromo-3-(substituted)-1,4-naphthoquninones. Amination reaction of 2,3-dihalo-1,4-naphthoquinones with aryl and aliphatic amines in ethanol gave 2-halo-3-(N-alkyl or N-aryl)-1,4-naphthoquinone derivatives (1a,b–10a,b) in 60%–90% yield. These derivatives subjected to antibacterial and antifungal activities,in vitro, againstBacillus subtilis ATCC 6633, Candida albicans 10231 and local, Pseudomonas aeruginosa NCTC10490, Staphylococcus aureus ATCC 6538p, Escherichia coli NIHJ, Aspergillus niger KCTC 1231. Tricophyton mentagrophytes KCTC 6085. Among these derivatives,1b, 6b and7a showed the potent antibacterial activities.1b, 8b and9b have the antifungal activities.1b is most effective in preventing the growth ofBacillus subtilis and Pseudomonas aeruginosa, Candida albicans, Aspergillus niger. Tricophyton mentagrophytes. The several of these compounds demonstrated a broad spectrum of activitiesin vitro.     

A new lignan glycoside from <Emphasis Type="Italic">Juniperus rigida</Emphasis>

A new lignan glycoside, named juniperigiside (1) was isolated from the CHCl₃ soluble fraction of the MeOH extract of stems and leaves of Juniperus rigida S.et Z. Compound 1 was identified by 1D- and 2D-NMR spectroscopy as well as CD analysis as (2R,3S)-2,3-dihydro-7-methoxy-2-(4′-hydroxy-3′-methoxyphenyl)-3-hydroxymethyl-5-benzofuranpropanol 4′-O-(3-O-methyl)-α-L-rhamnopyranoside. Five known lignans, icariside E4 (2), desoxypodophyllotoxin (3), savinin (4), thujastandin (5), and (−)-nortrachelogenin (6) in addition to five known labdane diterpenes including trans-communic acid (7), 13-epi-torulosal (8), 13-epi-cupressic acid (9), imbricatoric acid (10), and isocupressic acid (11) were also isolated and their structures were characterized by comparing their spectroscopic data with those in the literature. All compounds were isolated for the first time from this plant, and 5 and 6 were first reported from the genus Juniperus. The isolated compounds were tested for cytotoxicity against four human tumor cell lines in vitro using a Sulforhodamin B bioassay. Compounds 3, 4, 7, and 8 showed considerable cytotoxicity against four human cancer cell lines in vitro.     

Synthesis and antiviral activity of new 4-(phenylamino)/4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acids derivatives

The synthesis of new 4-(phenylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid (3a-l) derivatives and the new 4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acid (5a–c) derivatives was achieved with an efficient synthetic route. Ethyl 4-chloro-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate (1) on fusion with appropriate substituted anilines or aminopicolines gave the required new ethyl 4-(phenylamino)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylates (2a–l) (52–82%) or new ethyl 4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylates (4a–c) (50–60%), respectively. Subsequent hydrolysis of the esters afforded the corresponding carboxylic acids (3a–l) (86–93%) and (5a–c) in high yield (80–93%). Inhibitory effects of 4-(phenylamino)/4-[(methylpyridin-2-yl)amino]-1-phenyl-1H-pyrazolo[3,4-b]pyridine-4-carboxylic acids. Derivatives on Herpes simplex virus type 1 (HSV-1), Mayaro virus (MAY) and vesicular stomatitis virus (VSV) were investigated. Compounds 2d, 3f, 3a, and 3c exhibited antiviral activity against HSV-1, MAY, and VSV virus with EC₅₀ values of 6.8, 2.2, 4.8, 0.52, 2.5, and 1.0. None of these compounds showed toxicity for Vero cells.