Bioactive saponins with cancer related and immunomodulatory activity: Recent developments

Effect of Saengmaeksan on Fatigue, Liver Function, and Immunity Combined with High-Intensity Training

Saengmaeksan (SMS) is a traditional drink that consists of three natural herbs, Lirio platyphlla, Panax ginseng, and Schisandra chinensis, and improves fatigue, liver function, and immunity. Moderate-intensity exercise has a positive effect on fatigue, liver function, and immune function, whereas long-term high-intensity training has a negative effect on these aspects. We hypothesized that SMS intake will improve fatigue (ammonia, lactic acid), liver function (aspartate transaminidase (AST) and alanine aminotransferase (ALT)), and immunity (IgA, IgG, IgM) with high-intensity training. To investigate this hypothesis, 17 male college tennis players were randomly assigned to SMS and placebo groups with high-intensity training. SMS and placebo were consumed in 110 mL doses for a total of 770 mL. High-intensity training was performed at 70%-90% of heart rate reserve, conducted five times weekly for 4 weeks. A significant interaction effect was observed between the SMS and control (CON) groups regarding ammonia, ALT, and IgA levels. Ammonia levels significantly decreased in the SMS group, but there was no difference in the lactic acid levels. AST significantly decreased in the SMS group. IgA significantly increased in the SMS group, IgM significantly decreased in both groups, but there was no change in IgG. The correlation analysis revealed positive correlation in ΔAST vs. ΔALT, ΔALT vs. ΔIgG, and ΔIgA vs. ΔIgG in the SMS group. These findings demonstrate that SMS intake can reduce ammonia, AST, ALT, and IgM levels, while causing an increase in IgA, which has a positive effect on fatigue reduction, liver function, and immunoglobulins in a high-intensity training or related environment.

Shatavarin-IV saponin adjuvant elicits IgG and IgG2b responses against Staphylococcus aureus bacterin in a murine model

Asparagus adscendens Roxb. also known as "safed musli" or "shatavari" is a medicinal plant commonly found in South Asian countries. Shatavari is effective for the treatment of gastric ulcers, renal stones, bronchitis, diabetes, diabetic neuropathy, irritable bowel syndrome, alcohol withdrawal and has reported immunostimulatory effects. In this study, the adjuvant potential of Shatavarin-IV saponin against Staphylococcus aureus bacterin in mice was investigated. Shatavarin-IV was evaluated for its toxicity and immunomodulatory potential against S. aureus bacterin in mice. Cellular and humoral immune responses were assessed. Shatavarin-IV was isolated from the fruit extract of Asparagus adscendens. The confirmation of the isolated molecule as Shatavarin-IV was done via TLC-based comparison with the standard molecule. Further, the structure was confirmed by using extensive spectroscopic analyses and comparing the observed data with literature reports. It was found safe up to the dose of 0.1 mg in the mice model. Shatavarin-IV adjuvant elicited IgG and IgG2b responses at the dose of 40 μg against S. aureus bacterin. However, the cell-mediated immune response was lesser as compared with the commercial Quil-A saponin . We demonstrated that Shatavarin-IV saponin adjuvant produced an optimum humoral immune response against S. aureus bacterin. These results highlight the potential of Shatavarin-IV as an adjuvant in a combination adjuvant in vaccine formulations for induction of potent immune response.

A non-polar fraction of Saponaria officinalis L. acted as a TLR4/MD2 complex antagonist and inhibited TLR4/MyD88 signaling in vitro and in vivo

Targeting Toll-like receptor 4/myeloid differentiation factor 2 (TLR4/MD2) signaling is regarded as a potential strategy for treating inflammatory diseases. Saponaria officinalis L. is rich in saponin, which include quillaic acid, gypsogenin, saponarin, and hederagenin. We evaluated the pharmacological activity of a Saponaria officinalis extract in THP-1 derived macrophages and RAW264.7 macrophages. TLR4/MyD88 complex formation and downstream signals were investigated by co-immunoprecipitation (Co-IP). In silico docking simulation was conducted to predict binding scores and perform 3D modeling of saponarin-TLR4/MD2 complex. A hexane fraction of Saponaria officinalis (SH) and fr.1 (a sub-fraction 1 of SH) inhibited mitogen-activated protein kinase (MAPK) signaling, nuclear factor kappa b (NF-κB) activity, cytokine production, and the expressions of marker genes specific for M1 polarization. The inhibitory effects of fr.1 and saponarin on TLR4/MyD88 complex formation were observed by western blotting TLR4 co-immunoprecipitated proteins. Saponarin and fr.1 markedly attenuated LPS-induced inflammatory cytokines, thus reducing mortality and morphological abnormality in zebrafish larvae. Finally, docking simulation revealed that saponarin can directly interact with TLR4/MD2 complex to inhibit downstream signalings. Our findings suggest that saponarin reduces downstream inflammatory response by disrupting TLR4/MD2 complex and blocking MyD88-dependent inflammatory signaling.

Saponin and chitosan-based oral vaccine against viral haemorrhagic septicaemia virus (VHSV) provides protective immunity in olive flounder (Paralichthys olivaceus)

Production losses of olive flounder (Paralichthys olivaceus) have increased owing to viral haemorrhagic septicaemia virus (VHSV) infection. In this study, we determined safe concentrations of orally administered saponin and chitosan by analysing serum enzyme (AST/ALT) levels as biochemical markers of hepatic injury. Furthermore, we demonstrated the efficacy, duration of protection, and safety of saponin and chitosan-based vaccines with inactivated VHSV (IV). Oral administration of saponin, chitosan, and their combination did not induce fish mortality at all tested concentrations (0.29, 1.45, and 2.9 mg/g of fish body weight/day) 10 days after administration. However, AST level was high at a dose >0.29 mg/g of fish body weight/day. Both saponin and chitosan were found to be safe and acceptable for vaccination studies at a dose of 0.29 mg/g of fish body weight/day. Administration of IV alone did not induce protection at 2 and 4 weeks post vaccination (wpv). Olive flounders administered saponin + IV and chitosan + IV vaccines had higher immunity against VHSV with relative percentage survival (RPS) of 12.5-7.5% and 0-20.1%, respectively; however, additional immunisation with combination of saponin + chitosan + IV clearly enhanced the protection with RPS values of 10-15%, 26.7%, 42.9%, and 37.5% at 4, 8, 12, and 20 wpv, respectively. Although the RPS value of oral immunisation was not comparable to that of injectable vaccines, the manufacturing process is simple and oral administration causes less stress to juvenile fish. To investigate the development of a protective immune response, olive flounder were re-challenged with VHSV (10^7.8 TCID₅₀/fish) at 70 days postinfection; 100% of the previously unexposed fish died, whereas 80-100% of the previously immunised fish survived. Our results showed the possibility of developing preventive measures against VHSV using saponin and chitosan-based oral vaccines with inactivated virus.

Spirostanol Saponins from Flowers of Allium Porrum and Related Compounds Indicating Cytotoxic Activity and Affecting Nitric Oxide Production Inhibitory Effect in Peritoneal Macrophages

Saponins, a diverse group of natural compounds, offer an interesting pool of derivatives with biomedical application. In this study, three structurally related spirostanol saponins were isolated and identified from the leek flowers of Allium porrum L. (garden leek). Two of them were identical with the already known leek plant constituents: aginoside (1) and 6-deoxyaginoside (2). The third one was identified as new component of A. porrum; however, it was found identical with yayoisaponin A (3) obtained earlier from a mutant of elephant garlic Allium ampeloprasun L. It is a derivative of the aginoside (1) with additional glucose in its glycosidic chain, identified by MS and NMR analysis as (2α, 3β, 6β, 25R)-2,6-dihydroxyspirostan-3-yl β-D-glucopyranosyl-(1 → 3)-β-D-glucopranosyl-(1 → 2)-[β-D-xylopyranosyl-(1 → 3)]-β-D-glucopyranosyl]-(1 → 4)-β-D-galactopyranoside, previously reported also under the name alliporin. The leek native saponins were tested together with other known and structurally related saponins (tomatonin and digitonin) and with their related aglycones (agigenin and diosgenin) for in vitro cytotoxicity and for effects on NO production in mouse peritoneal cells. The highest inhibitory effects were exhibited by 6-deoxyaginoside. The obtained toxicity data, however, closely correlated with the suppression of NO production. Therefore, an unambiguous linking of obtained bioactivities of saponins with their expected immunobiological properties remained uncertain.

Two new triterpenoid saponins: telephiifoliosides A and B from the roots of Corrigiola litoralis subsp. telephiifolia (Pourr.) Briq

The polar fraction of the MeOH extract of the roots of Corrigiola litoralis subsp. telephiifolia (Pourr.) Briq. (Caryophyllaceae) was investigated for its constituents and two previously unreported monodesmosides triterpene saponins, telephiifoliosides A and B (1 and 2), along with the known bonushenricoside A (3) were isolated. Their structures were elucidated by combined spectroscopic and spectrometric techniques (¹H NMR, ¹³C NMR, HSQC, ¹H-¹H COSY, HMBC, TOCSY, NOESY, HRESIMS) and chemical methods. The structures of the new saponins were established as; 3-O-α-L-arabinopyranosyljaligonic acid (1), and 3-O-α-L-arabinopyranosylphytolaccagenin ester (2). Upon evaluation of the antiproliferative activity on human malignant epithelial (HeLa) cells, none of the isolated compounds was efficient at the concentration of 33 µM. HighlightsThis is the first phytochemical study on Corrigiola litoralis subsp. telephiifolia.Two new saponins were isolated from the roots of Corrigiola litoralis subsp. telephiifolia.The isolated compounds were tested for their antiproliferative activity.

Updated insights into the mechanism of action and clinical profile of the immunoadjuvant QS-21: A review

BACKGROUND

Vaccine adjuvants are compounds that significantly enhance/prolong the immune response to a co-administered antigen. The limitations of the use of aluminium salts that are unable to elicite cell responses against intracellular pathogens such as those causing malaria, tuberculosis, or AIDS, have driven the development of new alternative adjuvants such as QS-21, a triterpene saponin purified from Quillaja saponaria.

PURPOSE

The aim of this review is to attempt to clarify the mechanism of action of QS-21 through either receptors or signaling pathways in vitro and in vivo with special emphasis on the co-administration with other immunostimulants in new adjuvant formulations, called adjuvant systems (AS). Furthermore, the most relevant clinical applications will be presented.

METHODS

A literature search covering the period 2014-2018 was performed using electronic databases from Sci finder, Science direct, Medline/Pubmed, Scopus, Google scholar.

RESULTS

Insights into the mechanism of action of QS-21 can be summarized as follows: 1) in vivo stimulation of Th2 humoral and Th1 cell-mediated immune responses through action on antigen presenting cells (APCs) and T cells, leading to release of Th1 cytokines participating in the elimination of intracellular pathogens. 2) activation of the NLRP3 inflammasome in mouse APCs with subsequent release of caspase-1 dependent cytokines, Il-1β and Il-18, important for Th1 responses. 3) synthesis of nearly 50 QS-21 analogs, allowing structure/activity relationships and mechanistic studies. 4) unique synergy mechanism between monophosphoryl lipid A (MPL A) and QS-21, formulated in a liposome (AS01) in the early IFN-γ response, promoting vaccine immunogenicity. The second part of the review is related to phase I-III clinical trials of QS-21, mostly formulated in ASs, to evaluate efficacy, immunogenicity and safety of adjuvanted prophylactic vaccines against infectious diseases, e.g. malaria, herpes zoster, tuberculosis, AIDS and therapeutic vaccines against cancer and Alzheimer's disease.

CONCLUSION

The most advanced phase III clinical applications led to the development of two vaccines containing QS-21 as part of the AS, the Herpes Zoster vaccine (HZ/su) (Shingrix™) which received a license in 2017 from the FDA and a marketing authorization in the EU in 2018 and the RTS,S/AS01 vaccine (Mosquirix™) against malaria, which was approved by the EMA in 2015 for further implementation in Sub-Saharan countries for routine use.

Phytochemistry of Weigela x “kosteriana variegata” (Caprifoliaceae)

One new triterpene glycoside 3- O-β-D-xylopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→3)]-β-D-xylopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid, was isolated from Weigela x “kosteriana variegata” (Caprifoliaceae), with three known ones. Their structures were characterized by a combination of mass spectrometry and 1D and 2D NMR spectrocopic techniques including 1H- and 13C NMR, COSY, TOCSY, NOESY, HSQC, and HMBC experiments. The toxicological properties of some glycosides were determined with a zebrafish-based assay. The results show that the most active compounds were toxic to the larvae in the range of 1 μM.

New perspectives for natural triterpene glycosides as potential adjuvants

BACKGROUND

Triterpene glycosides are a vast group of secondary metabolites widely distributed in plants including a high number of biologically active compounds. The pharmacological potential is evaluated by using many bioassays particularly in the field of cancerology, immunology, and microbiology. The adjuvant concept is well known for these molecules in vaccines, but there is little preclinical evidence to support this concept in the management of cancer, infections and inflammation.

PURPOSE

We aim to review some examples of triterpene glycosides from natural sources which exhibit adjuvant activity when they are co-adminitered with anticancer drugs, targeted toxins, antimicrobial, anti-inflammatory drugs and with antigens in vaccines.

METHODS

The scientific literature on the adjuvant potential of triterpene glycosides covering mainly the last two decades has been identified by using relevant key words in the databases, using the online service such as Medline/PubMed, Scopus, Web of Science, Google Scholar.

RESULTS

We divided these findings in four kind of examples, the combination of triterpene glycosides (1) with chemotherapeutic agents in conventional tumor therapies and with targeted toxins, (2) with antimicrobial drugs, (3) with antiinflammatory drugs, and (4) with an antigen in prophylactic and therapeutic vaccines. Pharmacological studies have revealed that some triterpene glycosides co-administered with anticancer drugs such as cisplatin, paclitaxel, cyclophosphamide, etoposide, 5-fluorouracyl, mitoxantrone exhibited increased cytotoxicity in tumor cells better than when the drugs were administered alone. However in vivo toxicological and pharmacokinetic studies are required before the combination strategy can be applied into clinical practice. Other studies showed that combined application of triterpene glycosides with targeted toxins resulted in the increased efficacy of the toxin, simultaneously reducing the dosage, and side effects. It was also shown that the co-administration of the triterpenoids with corticosteroids synergistically inhibited the inflammatory response induced by carrageenan in rats. The search for new alternative adjuvants in vaccines in comparison with the aluminium salts inducing only a Th2-type immune response resulted in the discovery of the promising purified fraction QS-21 from Quillaja saponaria, which has been used in the development of a variety of prophylactic and therapeutic vaccines. Over 120 clinical trials for around 20 vaccine indications in infectious diseases, cancer, degenerative disorders have been reported involving more than 50,000 patients.

CONCLUSION

This review summarized the successfull in vitro and in vivo studies showing that this combination approach of triterpene glycosides co-adminitered with anticancer, antimicrobial and anti-inflammatory drug may provide an exciting road for further developments in the treatment of some cancers, parasitic and inflammatory diseases and in the rational design of vaccines against infectious diseases and cancer. From a clinical point of view, the potential benefit of QS-21, a promising triterpene glycoside from Quillaja saponaria has been highlighted in several vaccine clinical trials with a favorable ratio efficacy/toxicity.

Six new furostanol glycosides from Smilax glauco-china and their cytotoxic activity

Six new steroidal saponins, namely glauco-chinaosides A-F, and one known compound were isolated from the tubers of Smilax glauco-china. Their structures were elucidated by a combination of spectroscopic analysis and hydrolysis followed by spectral and chromatographic analysis. Compounds 1-7 were tested in vitro for their cytotoxic activities against four human tumor cell lines (SH-SY5Y, SGC-7901, HCT-116, and Lovo). Compounds 1, 2, and 5 exhibited cytotoxic activity against SGC-7901, with IC₅₀ values of 2.7, 11.5, and 6.8 μM, respectively.

3-Keto umbilicagenin A and B, new sapogenins from Allium umbilicatum Boiss

Two sapogenins, named 3-keto umbilicagenin A and B (1 and 2), possessing a novel chemical structure with a 3-keto group on the spirostane skeleton, have been isolated from Allium umbilicatum Boiss. Their chemical structure has been established through a combination of extensive spectroscopic analysis, mainly nuclear magnetic resonance and mass spectrometry, and chemical methods as (25R)-3-keto-spirostan-2α,5α,6β-triol (1) and (25R)-3-keto-spirostan-2α,5α-diol (2). The isolated compounds were tested for cytotoxic activity on J-774, murine monocyte/macrophage, and WEHI-164, murine fibrosarcoma cell lines.

Triterpenoid saponins from the roots of two Gypsophila species

Two triterpenoid saponins with two known ones have been isolated from the roots of Gypsophila arrostii var. nebulosa, and two new ones from the roots of Gypsophila bicolor. Their structures were established by extensive NMR and mass spectroscopic techniques as 3-O-β-d-galactopyranosyl-(1→2)-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosylquillaic acid 28-O-β-d-xylopyranosyl-(1→4)-[β-d-glucopyranosyl-(1→3)]-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-fucopyranosyl ester (1), 3-O-β-d-galactopyranosyl-(1→2)-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosylgypsogenin 28-O-β-d-xylopyranosyl-(1→4)-[β-d-glucopyranosyl-(1→3)]-α-l-rhamnopyranosyl-(1→2)-[β-d-glucopyranosyl-(1→4)]-β-d-fucopyranosyl ester (2), 3-O-β-d-galactopyranosyl-(1→2)-[β-d-xylopyranosyl-(1→3)]-β-d-glucuronopyranosylgypsogenin 28-O-β-d-xylopyranosyl-(1→3)-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-[(4-O-acetyl)-β-d-quinovopyranosyl-(1→4)]-β-d-fucopyranosyl ester (3), gypsogenic acid 28-O-β-d-glucopyranosyl-(1→3)-{6-O-[3-hydroxy-3-methylglutaryl]-β-d-glucopyranosyl-(1→6)}-β-d-galactopyranosyl ester (4). Three compounds were evaluated against one human colon cancer cell line SW480 and one rat cardiomyoblast cell line H9c2.

Triterpenoid saponins from Polycarpaea corymbosa Lamk. var. eriantha Hochst

Four triterpenoid saponins (1-4) were isolated from Polycarpaea corymbosa Lamk. var. eriantha Hochst along with the known apoanagallosaponin IV (5). Their structures were elucidated by spectroscopic data analysis. Among the compounds 1, 3-5 which were evaluated for their cytotoxicity against three tumor cell lines (SW480, DU145 and EMT6), compound 1 exhibited cytotoxicity with IC50 values ranging from 4.61 to 22.61 μM, which was greater than that of etoposide. Compound 2 was tested only against SW480 and a cardiomyoblast cell line (H9c2), and was inactive.

Assessment of antioxidant and cytotoxicity activities of saponin and crude extracts of Chlorophytum borivilianum

The present paper focused on antioxidant and cytotoxicity assessment of crude and total saponin fraction of Chlorophytum borivilianum as an important medicinal plant. In this study, three different antioxidant activities (2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), ferrous ion chelating (FIC), and β -carotene bleaching (BCB) activity) of crude extract and total saponin fraction of C. borivilianum tubers were performed. Crude extract was found to possess higher free radical scavenging activity (ascorbic acid equivalents 2578 ± 111 mg AA/100 g) and bleaching activity (IC50 = 0.7 mg mL(-1)), while total saponin fraction displayed higher ferrous ion chelating (EC50 = 1 mg mL(-1)). Cytotoxicity evaluation of crude extract and total saponin fraction against MCF-7, PC3, and HCT-116 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) cell viability assay indicated a higher cytotoxicity activity of the crude extract than the total saponin fraction on all cell lines, being most effective and selective on MCF-7 human breast cancer cell line.

Triterpene saponins from Antonia ovata leaves

Six pentacyclic triterpenoid saponins, named antoniosides E-J along with two known alkaloids, were isolated from the leaves of Antonia ovata. Their structures were determined by the extensive use of 1D and 2D-NMR experiments along with HRESIMS analysis and acid hydrolysis. All isolated saponins contained the same pentasaccharide chain: 3-O-[β-D-glucopyranosyl-(1→2)]-[β-D-glucopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl(1→6)]-β-D-glucopyranoside, linked at C-3 of esterified derivatives of polyhydroxyoleanene triterpenoids (theasapogenol A and 15α-hydroxy-theasapogenol A). Isolated compounds were evaluated for their cytotoxic activity against KB cell line by a WST-1 assay, and the IC(50) values ranged from 3.3 to 5.3 μM.

Triterpenoid saponins from Hydrocotyle bonariensis Lam

Phytochemical investigation of the under-ground parts of Hydrocotyle bonariensis led to the isolation of five oleanane-type triterpenoid saponins, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-22-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-(2-methylbutyroyl)-28-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-21-O-acetyl-R(1)-barrigenol, 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-R(1)-barrigenol, and 3-O-{β-D-glucopyranosyl-(1 → 2)-[α-L-arabinopyranosyl-(1 → 3)]-β-D-glucuronopyranosyl}-22-O-(2-methylbutyroyl)-A(1)-barrigenol, together with the known saniculoside-R1. Their structures were established by 2D NMR techniques and mass spectrometry. Six compounds were evaluated against two human colon cancer cell lines, HCT 116 and HT-29. Two compounds showed weak cytotoxicity with IC(50) 24.1 and 24.0, 83.0 and 83.6 μM against HT-29 and HCT 116, respectively.

Carbohydrate-based immune adjuvants

The role for adjuvants in human vaccines has been a matter of vigorous scientific debate, with the field hindered by the fact that for over 80 years, aluminum salts were the only adjuvants approved for human use. To this day, alum-based adjuvants, alone or combined with additional immune activators, remain the only adjuvants approved for use in the USA. This situation has not been helped by the fact that the mechanism of action of most adjuvants has been poorly understood. A relative lack of resources and funding for adjuvant development has only helped to maintain alum's relative monopoly. To seriously challenge alum's supremacy a new adjuvant has many major hurdles to overcome, not least being alum's simplicity, tolerability, safety record and minimal cost. Carbohydrate structures play critical roles in immune system function and carbohydrates also have the virtue of a strong safety and tolerability record. A number of carbohydrate compounds from plant, bacterial, yeast and synthetic sources have emerged as promising vaccine adjuvant candidates. Carbohydrates are readily biodegradable and therefore unlikely to cause problems of long-term tissue deposits seen with alum adjuvants. Above all, the Holy Grail of human adjuvant development is to identify a compound that combines potent vaccine enhancement with maximum tolerability and safety. This has proved to be a tough challenge for many adjuvant contenders. Nevertheless, carbohydrate-based compounds have many favorable properties that could place them in a unique position to challenge alum's monopoly over human vaccine usage.

Cytotoxicity and inhibition of DNA topoisomerase I of polyhydroxylated triterpenoids and triterpenoid glycosides

Cytotoxicity and inhibition on human DNA topoisomerase I (TOP1) and II (TOP2) of 74 plant-originated triterpenoids and triterpenoid glycosides were investigated. The cytotoxic compounds are primarily polyhydroxylated oleananes (GI(50) of A549: 1.0-10.19 microM). Sixteen cytotoxic aesculiosides isolated from Aesculus pavia inhibited TOP1 catalytic activity by interacting directly with the free enzyme and preventing the formation of the DNA-TOP1 complex. Interestingly, hydrolysis of six active aesculiosides (1, 4, 6, 8, 10, and 23) lost their TOP1 activities but enhanced their cytotoxicities. None of the test compounds showed any activity against TOP2. Structure-activity relationship (SAR) investigations indicated that cytotoxic oleananes required at least one angeloyl moiety at either C-21 or C-22 but the sugar moiety at C-3 may decrease their cytotoxicities. An angeloyl or tigeloyl group at C-21 is required for oleananes to bind the free TOP1 enzyme although the type and length of acyl moiety at C-22 also affects their activity. However, sugar moiety at C-3 is necessary for their TOP1 activities.

Advances in saponin-based adjuvants

Saponins are natural glycosides of steroid or triterpene which exhibited many different biological and pharmacological activities. Notably, saponins can also activate the mammalian immune system, which have led to significant interest in their potential as vaccine adjuvants. The most widely used saponin-based adjuvants are Quil A and its derivatives QS-21, isolated from the bark of Quillaja saponaria Molina, which have been evaluated in numerous clinical trials. Their unique capacity to stimulate both the Th1 immune response and the production of cytotoxic T-lymphocytes (CTLs) against exogenous antigens makes them ideal for use in subunit vaccines and vaccines directed against intracellular pathogens as well as for therapeutic cancer vaccines. However, Quillaja saponins have serious drawbacks such as high toxicity, undesirable haemolytic effect and instability in aqueous phase, which limits their use as adjuvant in vaccination. It has driven much research for saponin-based adjuvant from other kinds of natural products. This review will summarize the current advances concerning adjuvant effects of different kinds of saponins. The structure-activity relationship of saponin adjuvants will also be discussed in the light of recent findings. It is hoped that the information collated here will provide the reader with information regarding the adjuvant potential applications of saponins and stimulate further research into these compounds.

Immunorestoration and augmentation of mitogen lymphocyte response in Graffi tumor bearing hamsters by purified saponin mixture from Astragalus corniculatus

Investigations on the effect of purified saponin mixture (PSM) obtained from the aerial parts of Astragalus corniculatus Bieb. (Fabaceae) on mitogen response of the spleen cells in Graffi tumor bearing (GTBH) and healthy hamsters were reported. The saponin mixture in a doses of 50mg/kg b.w. was injected i.p. 4 times starting simultaneously with implantation of tumor cells. Stimulation indices to phytohemagglutinine (PHA) and lipopolysaccharide (LPS) of lymphocytes in spleens of tumor bearing hamsters (TBH) were significantly decreased during the whole period of the observation. It was established that PSM stimulated the functions of spleen cells in Graffi-TBH, resulting in increased mitogen response to PHA and LPS. The stimulation was better expressed in healthy PSM-treated hamsters. The proliferation response of spleen lymphocytes to PSM was also found. PSM did not change the in vitro proliferation ability of Graffi tumor cells. The results obtained proved the immunostimulating and immunorestorating activity of PSM on the T- and B-spleen cells in healthy and GTBH hamsters, as well as the proliferative response of it to PSM.

Intramolecular interchain reactions in bidesmosidic glycosides, a new insight into carbohydrate rearrangements induced by electrospray ionisation

Glycoconjugates are a class of complex molecules that are widely distributed in the plant kingdom and in some marine organisms. This class of compounds has a wide range of biological activities such as anti-inflammatory, antimicrobial, antifungal, anticancer, antiulcer, and immunoenhancing actions.1-3 Some of them also show various toxic activities such as cytotoxic, hemolytic, cardiotoxic, and teratogenic. Among these compounds, steroidal and triterpenoid saponins have long been known as components of widely used herbal drugs and pharmaceutical preparations; ginseng, Tribulus terrestris, Quillaja saponaria, and Digitalis ssp. are just a few examples. Thus, identification of saponins in herbal drugs used worldwide is of significance in phytochemical and toxicological quality control studies, and for the production of safe health products. Therefore, there is continuing demand for methods to rapidly identify and characterize these natural products.