Preparation of a chemically sulfated polysaccharide derived from Grifola frondosa and its potential biological activities

This report describes the preparation, characterization and potential biological activities of a chemically sulfated polysaccharide (S-GAP-P), which was derived from water-insoluble polysaccharide of Grifola frondosa mycelia. S-GAP-P was determined to be a glucan sulfate with the average molecular weight of 28 kDa and the sulfur content of 16.4%. The antitumor and immunomodulating activities of the sulfated derivative were estimated in vitro and in vivo. S-GAP-P inhibited the proliferation of SGC-7901 cells and induced apoptosis, in a dose-dependent manner. And the results from in vivo experiments demonstrated that S-GAP-P significantly inhibited the tumor growth and enhanced the peritoneal macrophages phagocytosis in S180-bearing mice. It is noteworthy that S-GAP-P could accelerate the antitumor activity of CTX and improve the immunocompetence damaged by CTX, suggesting the combination might increase cytotoxic efficacy and decrease toxicity of some chemotherapeutic agents in cancer treatment.     

In vitro antiplasmodial activity of extract and constituents from Esenbeckia febrifuga, a plant traditionally used to treat malaria in the Brazilian Amazon

Esenbeckia febrifuga (Rutaceae) is a plant traditionally used to treat malaria in the Brazilian Amazon region. Ethanol extract of stems displayed a good antiplasmodial activity against Plasmodium falciparum strains W-2 (IC₅₀ 15.5±0.71 μg/ml) and 3 D7 (IC₅₀ 21.0±1.4 μg/ml). Two coumarins (bergaptene 1 and isopimpinellin 2), five alkaloids (flindersiamine 3, kokusaginine 4, skimmiamine 5, γ-fagarine 6 and 1-hydroxy-3-methoxy-N-methylacridone, 7), besides a limonoid (rutaevine 8), have been isolated for the first time from this species. Antiplasmodial activity of compounds 3, 5–8 has been evaluated in vitro against P. falciparum strains (W-2 and 3D7) and the furoquinolines 5 and 6 were the most potent displaying IC₅₀ values <50 μg/ml; flindersiamine (3) showed a weak activity while alkaloid 7 and rutaevine (8) were inactive (IC₅₀>100 μg/ml).     

Anti-proliferative lichen compounds with inhibitory activity on 12(S)-HETE production in human platelets

Several lichen compounds, i.e. lobaric acid (1), a β-orcinol depsidone from Stereocaulon alpinum L., (+)-protolichesterinic acid (2), an aliphatic -methylene-γ-lactone from Cetraria islandica Laur. (Parmeliaceae), (+)-usnic acid (3), a dibenzofuran from Cladonia arbuscula (Wallr.) Rabenh. (Cladoniaceae), parietin (4), an anthraquinone from Xanthoria elegans (Link) Th. Fr. (Calaplacaceae) and baeomycesic acid (5), a β-orcinol depside isolated from Thamnolia vermicularis (Sw.) Schaer. var. subuliformis (Ehrh.) Schaer. were tested for inhibitory activity on platelet-type 12(S)-lipoxygenase using a cell-based in vitro system in human platelets. Lobaric acid (1) and (+)-protolichesterinic acid (2) proved to be pronounced inhibitors of platelet-type 12(S)-lipoxygenase, whereas baeomycesic acid (5) showed only weak activity (inhibitory activity at a concentration of 100 μg/ml: 1 93.4±6.62%, 2 98,5±1.19%, 5 14.7±2.76%). Usnic acid (3) and parietin (4) were not active at this concentration. 1 and 2 showed a clear dose–response relationship in the range of 3.33–100 μg/ml. According to the calculated IC₅₀ values the highest inhibitory activity was observed for the depsidone 1 (IC₅₀=28.5 μM) followed by 2 (IC₅₀=77.0 μM). The activity of 1 was comparable to that of the flavone baicalein, which is known as a selective 12(S)-lipoxygenase inhibitor (IC₅₀=24.6 μM).     

Simultaneous determination of 5-fluorouracil and uracil by high-performance liquid chromatography using four serial columns

A sensitive assay was developed for the quantitation of 5-fluorouracil (5-FU) and uracil using liquid–liquid extraction (LLE) and HPLC with UV detection. Analyses were performed with four μBondapak C₁₈ columns connected in series using 20 mM acetic acid with 1% ACN as mobile phase. The calibration curves were linear across the range of 26–1000 ng ml⁻¹ (0.21–7.8 μM) for 5-FU and 1.0–14.0 μg ml⁻¹ (0.01–110 μM) for uracil. This assay has been implemented to determine the plasma concentrations for pharmacokinetic studies for 5-FU and uracil in conjunction with clinical trials.     

Synthesis, spectral studies and in vitro assessment for antiamoebic activity of new cyclooctadiene ruthenium(II) complexes with 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones

We report here the synthesis, characterization and in vitro antiamoebic activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones (TSC), 1–5, and their bidentate complexes [Ru(η⁴-C₈H₁₂)(TSC)Cl₂] 1a–5a. The biological studies of these compounds were investigated against HK-9 strain of Entamoeba histolytica and the concentration causing 50% cell growth inhibition (IC₅₀) was calculated in the micromolar range. The ligands exhibited antiamoebic activity in the range (2.05–5.29 μM). Screening results indicated that the potencies of the compounds increased by the incorporation of ruthenium(II) in the thiosemicarbazones. The complexes 1a–5a showed antiamoebic activity with an IC₅₀ of 0.61–1.43 μM and were better inhibitors of growth of E. histolytica, based on IC₅₀ values. The most promising among them is Ru(II) complex 2a having 1,2,3,4-tetrahydroquinoline as N⁴ substitution.     

Metal complexes of crosslinked chitosans Part II. An investigation of their hydrolysis to chitooligosaccharides using chitosanase

This paper investigates the behavior of crosslinked chitosans and metal-complexed crosslinked chitosans under similar hydrolytic conditions. Crosslinked chitosans with trimellitic anhydride, diisocyanatohexane, and dibromodecane as crosslinking agents under heterogenous reaction conditions were used as metal complexing agents by equilibrating them with metal salts such as ZnCl₂, MnSO₄, CuSO₄, CdSO₄, Pb(NO₃)₂, and HgCl₂. Crosslinked chitosan without metal complexation had the same hydrolytic behavior as uncrosslinked chitosan. However, when the crosslinked chitosans were complexed with metals, their rates of hydrolysis and extent of hydrolysis were significantly reduced. Thus, while for chitosan about 840 μg/ml reducing sugar was produced in 4 h time, and 780 μg/ml was produced for diisocyanatohexane crosslinked chitosan, only 400 μg/ml and 320 μg/ml reducing sugars were produced for cadmium sulfate with crosslinked chitosan and diisocyanatohexane crosslinked chitosan, respectively. Similar results are obtained for other crosslinking agents. Studies on preincubation of the metal with the enzyme show that of the metals studied, Mn has no effect on preincubatioin with the enzyme, Hg, Cd, Pb, and Cu completely deactivates the enzyme, while Zn reduces the enzyme activity by about 43.3%. Preincubation of the metal salts with the chitosan shows that Hg and Cu completely deactivate the molecule from enzyme hydrolysis, Cd and Zn inactivate it to the extent of 56.8% and 43.3%, respectively, while Mn has no effect. Availability of the amino functions seems to be a key feature for the chitosanase to hydrolyze the chitosan polymer. This was also proved by the significant increase in the extent of hydrolysis for chitosan samples with 88% (final value 1120 μg/ml reducing sugar) and 85% deacetylation (final value 840 μg/ml reducing sugar). HPIC studies of the products show that a variety of oligomers are produced in the chitosanase enzyme hydrolytic reaction.     

Effects of tannic acid and its related compounds on food mutagens or hydrogen peroxide-induced DNA strands breaks in human lymphocytes

The effect of tannic acid (TA), gallic acid (GA), propyl gallate (PA) and ellagic acid (EA) on DNA damage in human lymphocytes induced by food mutagens [3-amino-1-methyl-5H-pyrido (4,3-b) indole (Trp-P-2) and 2-amino-1-methyl-6-phenylimadazo (4,5-b) pyridine (PhIP) or H₂O₂ was evaluated by using single-cell electrophoresis (comet assay). The toxicity of these tested compounds (0.1–100 μg/ml) on lymphocytes was not found. These compounds did not cause DNA strand breaks at lower concentrations of 0.1–10 μg/ml. At a concentration of 100 μg/ml, TA and GA exhibited slight DNA damage, whereas PA and EA showed no DNA strand breaks. TA and its related compounds decreased the DNA strand breaks induced by Trp-P-2, PhIP or H₂O₂ at concentrations of 0.1–10 μg/ml. DNA repair enzymes endonuclease III (Endo III) and formamidopyrimidine-DNA glycoslase (FPG)] were used to examine the levels of oxidised pyrimidines and purines in human lymphocytes induced by H₂O₂. All the compounds at 10 μg/ml can reduce the level of FPG sensitive sites. However, only EA inhibited the formation of EndoIII sensitive sites. The results indicated that these compounds can enhance lymphocytes resistance towards DNA strand breaks induced by food mutagens or H₂O₂ in vitro.     

Synthesis, structure, and heterogeneous catalytic activity of tungsten chalcogenide cubane cluster containing alkaline earth metal complex

A new compound containing a cubane tungsten chalcogenide cluster [W₄(μ₃-Te)₄(CN)₁₂]⁶⁻ and Ca²⁺ complex units has been prepared by the reaction of aqueous solution of K₆[W₄(μ₃-Te)₄(CN)₁₂] · 5H₂O with the solution of a Ca(NO₃)₂ and phen(1,10-phenanthroline) (1:2 molar ratio) in a solvent mixture of H₂O/EtOH. The structure of [{Ca(phen)₂(H₂O)}{Ca(phen)(H₂O)₄}{Ca(phen)₂(H₂O)₃}][W₄Te₄(CN)₁₂] · 5H₂O 1 has been determined by X-ray crystallography. Compound 1 contains [{Ca(phen)(H₂O)₄}{Ca(phen)₂(H₂O)₃}][W₄(μ₃- Te)₄(CN)₁₂] units bridged by {Ca(phen)₂(H₂O)}²⁺ units to form an one-dimensional zigzag chain structure. Interestingly, compound 1 showed a heterogeneous catalytic activity in the transesterification of a range of esters with methanol under the mild conditions. Moreover, it can be reused without any loss of activity through 10 runs with ester.     

Synthesis, dihydrofolate reductase inhibition, antitumor testing, and molecular modeling study of some new 4(3H)-quinazolinone analogs

In order to produce potent new leads for anticancer drugs, a new series of quinazoline analogs was designed to resemble methotrexate (MTX, 1) structure features and fitted with functional groups believed to enhance inhibition of mammalian DHFR activity. Molecular modeling studies were used to assess the fit of these compounds within the active site of human DHFR. The synthesized compounds were evaluated for their ability to inhibit mammalian DHFR in vitro and for their antitumor activity in a standard in vitro tissue culture assay panel. Compounds 28, 30, and 31 were the most active DHFR inhibitors with IC₅₀ values of 0.5, 0.4, and 0.4 μM, respectively. The most active antitumor agents in this study were compounds 19, 31, 41, and 47 with median growth inhibitory concentrations (GI₅₀) of 20.1, 23.5, 26.7, and 9.1 μM, respectively. Of this series of compounds, only compound 31 combined antitumor potency with potent DHFR inhibition; the other active antitumor compounds (19, 41, and 47) all had DHFR IC₅₀ values above 15 μM, suggesting that they might exert their antitumor potency through some other mode of action. Alternatively, the compounds could differ significantly in uptake or concentration within mammalian cells.     

TOFA对人食管鳞癌Eca109和KYSE-450细胞生长的影响*

目的: 探讨5-十四烷氧基-2-呋喃酸(TOFA)对人食管鳞癌(ESCC)细胞Eca109和KYSE-450细胞增殖、周期和凋亡的影响。方法: 将Eca-109细胞和KYSE-450细胞分为对照组(DMSO)和实验组(TOFA),细胞(4×10³ cells/100 μl)接种于96孔板中,每个浓度设置5个复孔,培养24 h后,给予DMSO(对照)和不同浓度(1、3、5、10 μg/ml)TOFA处理,继续培养24、48和72 h;MTT检测细胞增殖,流式细胞术检测细胞周期和凋亡,Western blot检测p21、Cleaved caspase-3表达水平及p-AKT、p-mTOR、p-4EBP1修饰水平,专用试剂盒检测细胞内游离脂肪酸。结果: 与DMSO组比较,TOFA以浓度和时间依赖性方式抑制Eca109和KYSE-450细胞增殖(P均<0.05),处理48 h的IC₅₀分别为4.65和3.93 μg / ml;实验组细胞G2 / M 期细胞百分比增加,细胞凋亡率增高,p21、Cleaved caspase-3蛋白表达水平上调(P均<0.05),p-AKT、p-mTOR、p-4EBP1修饰水平下调(P均<0.05)。结论: TOFA抑制人食管鳞癌细胞增殖、阻滞细胞周期并促进细胞凋亡,其机制可能与其抑制AKT/mTOR/4EBP1信号通路有关。     

In vitro antiprotozoal activity of the lipophilic extracts of different parts of Turkish Pistacia vera L.

Thirteen lipophilic extracts prepared with n-hexane from various parts of Pistacia vera L. tree (Anacardiaceae) growing in Turkey were screened for their in vitro activity against four parasitic protozoa, Trypanosoma brucei rhodesiense, Trypanosoma cruzi, Leishmania donovani and Plasmodium falciparum. Melarsoprol, benznidazole, miltefosine, artemisinin and chloroquine were used as reference drugs. The cytotoxic potentials of the extracts on rat skeletal myoblast (L6) cells were also assessed and compared to that of podophyllotoxin. The screening method employed was medium-throughput, where the extracts were tested at two concentrations, at 0.8 and 4.8 μg/ml (T. brucei rhodesiense, L. donovani and Plasmodium falciparum), or at 1.6 and 9.7 μg/ml (T. cruzi and L6 cells). At 4.8 μg/ml concentration, the branch extract of Pistacia vera (PV-BR) significantly inhibited (77.3%) the growth of L. donovani, whereas the dry leaf extract (PV-DL) was active against Plasmodium falciparum (60.6% inhibition). The IC₅₀ values of these extracts were determined as 2.3 μg/ml (PV-BR, L. donovani) and 3.65 μg/ml (PV-DL, Plasmodium falciparum). None of the extracts possessed cytotoxicity on mammalian cells.     

Bioactive metabolites from the endophytic fungus Ampelomyces sp. isolated from the medicinal plant Urospermum picroides

Extracts of cultures grown in liquid or on solid rice media of the fungal endophyte Ampelomyces sp. isolated from the medicinal plant Urospermum picroides exhibited considerable cytotoxic activity when tested in vitro against L5178Y cells. Chromatographic separation yielded 14 natural products that were unequivocally identified based on their ¹H and ¹³C NMR as well as mass spectra and comparison with previously published data. Six compounds (2, 4, 5, 7, 9 and 11) were natural products. Both fungal extracts differed considerably in their secondary metabolites. The extract obtained from liquid cultures afforded a pyrone (2) and sulfated anthraquinones (7 and 9) along with the known compounds 1, 3, 6 and 8. When grown on solid rice medium the fungus yielded three compounds 4, 5 and 11 in addition to several known metabolites including 6, 8, 10, 12, 13 and 14. Compounds 4, 8 and 10 showed the strongest cytotoxic activity against L5178Y cells with EC₅₀ values ranging from 0.2–7.3 μg/ml. Furthermore, 8 and 10 displayed antimicrobial activity against the Gram-positive pathogens, Staphylococcus aureus, S. epidermidis and Enterococcus faecalis at minimal inhibitory concentrations (MIC) of 12.5 μg/ml and 12.5–25 μg/ml, respectively. Interestingly, 6 and 8 were also identified as constituents of an extract derived from a healthy plant sample of the host plant U. picroides thereby indicating that the production of bioactive natural products by the endophyte proceeds also under in situ conditions within the host plant.     

Modification at the C9 position of the marine natural product isoaaptamine and the impact on HIV-1, mycobacterial, and tumor cell activity

As part of an investigation to generate optimized drug leads from marine natural pharmacophores for the treatment of neoplastic and infectious diseases, a series of novel isoaaptamine analogs were prepared by coupling acyl halides to the C9 position of isoaaptamine (2) isolated from the Aaptos sponge. This library of new semisynthetic products was evaluated for biological activity against HIV-1, Mtb, AIDS-OI, tropical parasitic diseases, and cancer. Compound 4 showed potent activity against HIV-1 (EC₅₀ 0.47 μg/mL), compound 19 proved to possess remarkable activity against Mycobacterium intracellulare with an IC₅₀ and MIC value of 0.15 and 0.31 μg/mL, while compounds 4 and 17 possessed anti-leishmanial activity with IC₅₀ values of 0.1 and 0.4 μg/mL, respectively. Compounds 16 and 17 showed antimalarial activity with EC₅₀ values of 230 and 240 ng/mL, respectively, and compound 14 exhibited an EC₅₀ of 0.05 μM against the Leukemia cell line K-562.     

Anti-proliferative properties of prenylated flavonoids from hops (Humulus lupulus L.) in human prostate cancer cell lines

Chalcones xanthohumol (X) and desmethylxanthohumol (DMX), present in hops (Humulus lupulus L.), and the corresponding flavanones isoxanthohumol (IX, from X), 8-prenylnaringenin (8-PN, from DMX), and 6-prenylnaringenin (6-PN, from DMX), have been examined in vitro for their anti-proliferative activity on human prostate cancer cells PC-3 and DU145. X proved to be the most active compound in inhibiting the growth of the cell lines with IC₅₀ values of 12.3±1.1 μM for DU145 and 13.2±1.1 μM for PC-3. 6-PN was the second most active growth inhibitor, particularly in PC-3 cells (IC₅₀ of 18.4±1.2 μM). 8-PN, a highly potent phytoestrogen, exhibited pronounced anti-proliferative effects on PC-3 and DU145 (IC₅₀ of 33.5±1.0 and 43.1±1.2 μM, respectively), and IX gave comparable activities (IC₅₀ of 45.2±1.1 μM for PC-3 and 47.4±1.1 μM for DU145). DMX was the least active compound. It was evidenced for the first time that this family of prenylated flavonoids from hops effectively inhibits proliferation of prostate cancer cells in vitro.     

桦木酸对人胃癌SGC-7901细胞增殖的影响*

目的:利用不同浓度的桦木酸对人胃癌SGC-7901细胞增殖的影响。方法:桦木酸设4个不同浓度(0、10、20、30 μg/ml),并采用常规化疗药物5-Fu处理作为阳性对照,以探究其对细胞增殖的影响。采用台盼蓝拒染法和吉姆萨染色法分别检测桦木酸对人胃癌SGC-7901细胞生长抑制率及克隆形成率;EdU法检测SGC-7901的细胞增殖;利用流式细胞术检测细胞周期, 应用qRT-PCR和Western blot分别检测细胞周期蛋白cyclin D1,cyclin B1的mRNA和蛋白表达水平。结果:不同浓度的桦木酸处理人胃癌SGC-7901细胞48 h后,其细胞生长抑制率显著升高(P＜0.05),克隆形成率和细胞增殖率均明显降低(P＜0.01),且呈剂量和时间依赖性;人胃癌SGC-7901细胞被阻滞在G1/G0期,细胞周期蛋白cyclin D1和cyclin B1的mRNA和蛋白表达量也随桦木酸浓度升高而显著降低(P＜0.01)。且与5-Fu对照组相比,桦木酸浓度为20 μg/ml和30 μg/ml时,细胞增殖能力明显降低,细胞周期被抑制,细胞周期蛋白表达量均明显降低(P ＜0.05)。结论:桦木酸通过下调cyclin B1和cyclin D1基因表达,将人胃癌SGC-7901细胞阻滞在G1/G0期,从而抑制细胞增殖。     

Estrogen metabolism and formation of estrogen-DNA adducts in estradiol-treated MCF-10F cells. The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin induction and catechol-O-methyltransferase inhibition

Formation of estrogen metabolites that react with DNA is thought to be a mechanism of cancer initiation by estrogens. The estrogens estrone (E₁) and estradiol (E₂) can form catechol estrogen (CE) metabolites, catechol estrogen quinones [E₁(E₂)-3,4-Q], which react with DNA to form predominantly depurinating adducts. This may lead to mutations that initiate cancer. Catechol-O-methyltransferase (COMT) catalyzes an inactivation (protective) pathway for CE. This study investigated the effect of inhibiting COMT activity on the levels of depurinating 4-OHE₁(E₂)-1-N3Ade and 4-OHE₁(E₂)-1-N7Gua adducts in human breast epithelial cells. MCF-10F cells were treated with TCDD, a cytochrome P450 inducer, then with E₂ and Ro41-0960, a COMT inhibitor. Estrogen metabolites and depurinating DNA adducts in culture medium were analyzed by HPLC with electrochemical detection. Pre-treatment of cells with TCDD increased E₂ metabolism to 4-OHE₁(E₂) and 4-OCH₃E₁(E₂). Inclusion of Ro41-0960 and E₂ in the medium blocked formation of methoxy CE, and depurinating adducts were observed. With Ro41-0960, more adducts were detected in MCF-10F cells exposed to 1 μM E₂, whereas without the inhibitor, no increases in adducts were detected with E₂ ≤ 10 μM. We conclude that low COMT activity and increased formation of depurinating adducts can be critical factors leading to initiation of breast cancer.     

Antimicrobial and cytotoxic activity of 18 prenylated flavonoids isolated from medicinal plants: Morus alba L., Morus mongolica Schneider, Broussnetia papyrifera (L.) Vent, Sophora flavescens Ait and Echinosophora koreensis Nakai

Antimicrobial activity of the 18 prenylated flavonoids, which were purified from five different medicinal plants, was evaluated by determination of MIC using the broth microdilution methods against four bacterial and two fungal microorganisms (Candida albicans, Saccaromyces cerevisiae, Escherichia coli, Salmonella typhimurium, Staphylococcus epidermis and S. aureus). Papyriflavonol A, kuraridin, sophoraflavanone D and sophoraisoflavanone A exhibited a good antifungal activity with strong antibacterial activity. Kuwanon C, mulberrofuran G, albanol B, kenusanone A and sophoraflavanone G showed strong antibacterial activity with 5–30 μg/ml of MICs. Morusin, sanggenon B and D, kazinol B, kurarinone, kenusanone C and isosophoranone were effective to only gram positive bacteria, and broussochalcone A was effective to C. albicans. IC₅₀ values of papyriflavonol A, kuraridin, sophoraflavanone D, sophoraisoflavanone A and broussochalcone A in HepG2 cells were 20.9, 37.8, 39.1, 22.1, and 22.0 μg/ml, respectively. These results support the use of prenylated flavonoids in Asian traditional medicine to treat microbial infection and indicate a high potential for prenylated flavonoids as antimicrobial agents as well as anti-inflammatory agents.     

Protective effect of Ecklonia cava enzymatic extracts on hydrogen peroxide-induced cell damage

In this study, Ecklonia cava was enzymatically hydrolyzed to prepare water-soluble extracts, using five carbohydrases (Viscozyme, Celluclast, AMG, Termamyl, and Ultaraflo) and five proteases (Protamex, Kojizyme, Neutase, Flavourzyme, and Alcalase), and the potential antioxidant activity of each was assessed. The Celluclast and Viscozyme extracts of E. cava evidenced good hydrogen peroxide (H₂O₂) scavenging activities (73.25% and 72.92%, respectively) as compared to those of other enzymatic extracts. Therefore, the Celluclast enzymatic extract was selected for use in further experiments, and separated into four different molecular weight fractions (<1, 1–10, 10–30 and >30 kDa). Among these fractions, the >30 kDa fraction manifested the most profound H₂O₂ scavenging activity, with a measured IC₅₀ of 13 μg/ml. The >30 kDa fraction also strongly enhanced cell viability against H₂O₂-induced oxidative damage, and evidenced relatively good lipid peroxidation inhibitory activity in a Chinese hamster lung fibroblast (V79-4) cell line. This fraction also effected a reduction in the proportion of cells undergoing H₂O₂-induced apoptosis, as was demonstrated by a decreased quantity of sub-G₁ hypodiploid cells and decreased apoptotic body formation on the flow cytometry assay. These results clearly indicate that the >30 kDa fraction of E. cava possesses good antioxidant activity against H₂O₂ mediated cell damage in vitro.     

Antiviral property and mechanisms of a sulphated polysaccharide from the brown alga Sargassum patens against Herpes simplex virus type 1

A sulphated polysaccharide (SP-2a) from the brown alga Sargassum patens (Kütz.) Agardh (Sargassaceae) was found to significantly inhibit the in vitro replication of both the acyclovir (ACV)-sensitive and -resistant strains of Herpes simplex virus type 1 (HSV-1), in dose-dependent manners, with 50% inhibitions occurring with 1.5–5.3 μg/ml of the polysaccharide. SP-2a exhibited extracellular virucidal activity only against the ACV-sensitive strains, but not the resistant strain, at the concentration of 100 μg/ml. The strongest antiviral activities against the different strains of HSV-1 were observed when this polysaccharide was present during and after adsorption of the virus to host cells. The inhibitory effect of SP-2a on virus adsorption occurred dose-dependently in all the HSV-1 strains tested, and the adsorption of the ACV-resistant DM2.1 strain was reduced by 81.9% (relative to control) with 4 μg/ml of the polysaccharide. This study clearly demonstrated that the antiviral mode of action of SP-2a is mediated mainly by inhibiting virus attachment to host cells, and this sulphated polysaccharide might have different modes of action against the ACV-sensitive and -resistant strains of HSV-1.