Genotoxicity of an extract of Calendula officinalis L

Antimicrobial and Apoptotic Efficacy of Plant-Mediated Silver Nanoparticles

Phytogenically synthesised nanoparticle (NP)-based drug delivery systems have promising potential in the field of biopharmaceuticals. From the point of view of biomedical applications, such systems offer the small size, high surface area, and possible synergistic effects of NPs with embedded biomolecules. This article describes the synthesis of silver nanoparticles (Ag-NPs) using extracts from the flowers and leaves of tansy (Tanacetum vulgare L.), which is known as a remedy for many health problems, including cancer. The reducing power of the extracts was confirmed by total phenolic and flavonoid content and antioxidant tests. The Ag-NPs were characterised by various analytical techniques including UV-vis spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), Fourier transform infrared (FT-IR) spectroscopy, and a dynamic light scattering (DLS) system. The obtained Ag-NPs showed higher cytotoxic activity than the initial extracts against both human cervical cancer cell lines HeLa (ATCC CCL-2) and human melanoma cell lines A375 and SK-MEL-3 by MTT assay. However, the high toxicity to Vero cell culture (ATCC CCL-81) and human fibroblast cell line WS-1 rules out the possibility of their use as anticancer agents. The plant-mediated Ag-NPs were mostly bactericidal against tested strains with MBC/MIC index ≤4. Antifungal bioactivity (C. albicans, C. glabrata, and C. parapsilosis) was not observed for aqueous extracts (MIC > 8000 mg L^-1), but Ag-NPs synthesised using both the flowers and leaves of tansy were very potent against Candida spp., with MIC 15.6 and 7.8 µg mL^-1, respectively.

In vitro and in vivo evaluation of nanofibre mats containing Calendula officinalis extract as a wound dressing

OBJECTIVE

The present study aims to create Calendula officinalis-loaded nanofibre-based wound dressing materials to enhance the wound healing process. Calendula officinalis is an annual herb native to the Mediterranean region. It is antipyretic, antifungal, antioedema, antidiabetic, anti-inflammatory (wound, oral and pharyngeal mucosa), antispasmodic, treats chronic ocular surface diseases, acts as a stimulant and a diaphoretic. It is also used in the prevention of acute dermatitis, and in the treatment of gastrointestinal ulcers, wounds and burns.

METHOD

Electrospinning is an effective method for creating nano- and microfibres for biomedical applications. Calendula officinalis (CA) of various concentrations 5%, 10% and 15%)-loaded polyvinyl alcohol (PVA)/sodium alginate (SAlg) nanofibre mats were successfully produced via blend electrospinning. Nanofibre mats were evaluated using: scanning electron microscopy (SEM); Fourier transform infrared spectroscopy (FTIR) analysis; gel content; water vapour transmission rate (WVTR); swelling ratio; in vitro drug release studies; viability evaluation (cell culture and MTT assay); and an in vivo study using male Wistar rats. Rats were divided into three groups (n=3). In each group, rats were inflicted with five full-thickness wounds on the back and were treated with sterile gauze (control), PVA/SAlg nanofibre dressing (CA-free control), PVA/SAlg/CA5%, PVA/SAlg/CA10%, and PVA/SAlg/CA15% nanofibre dressing.

RESULTS

Results showed that the obtained fibres were smooth with no surface aggregates, indicating complete incorporation of Calendula officinalis. The release of Calendula officinalis from loaded PVA/SAlg fibre mats in the first four hours was burst released and then was constant. PVA/SAlg and PVA/SAlg/CA nanofibres were not toxic to L929 mouse fibroblasts and supported cell attachment and proliferation. The results of the in vivo study showed that the PVA/SAlg/CA10% nanofibre dressing had a higher full-thickness wound healing closure rate compared with the control group on days seven, 14 and 21 after treatment.

CONCLUSION

The results of this evaluation showed that PVA/SAlg/CA nanofibrous mats could be a candidate as an effective wound dressing; however, the percentage of CA in this compound needs further investigation.

In vitro evaluation of antioxidant activity and determination of total phenolic and flavonoids contents of ethanol-water extracts of Paeonia lactiflora and Calendula officinalis L. petals

In this study, the petals collected from peony hybrid Paeonia lactiflora "Bowl of beauty" and Calendula officinalis L. were extracted using ethanol-water mixture assisted with microwave and ultrasonic treatment. The isolation of Calendula officinalis L. essential oil was done by hydrodistillation as well. The total phenolic and flavonoids content in the extracts and oil were determined and their antioxidant activity was evaluated. The highest total phenolic content was found for the extracts of hybrid Paeonia lactiflora and Calendula officinalis L. obtained by ultrasound extraction (9.73 and 10.03 mg GA/mL RE, respectively), while the highest flavonoid content was obtained by microwave-assisted extraction (14.45 and 6.02 mg QE/mL RE, respectively). Antioxidant activity was assessed using standard antioxidant in vitro DPPH• and ABTS•+ assays. The highest antioxidant activity was obtained in DPPH• and ABTS•+ assay for the microwave-assisted extraction of hybrid Paeonia lactiflora (79% and 83%) and ultrasound-assisted extraction of Calendula officinalis L. (45% and 49%), respectively. In order to improve the antioxidative activity of both extract and essential oil the pectin films with gallic acid, using enzymatically assisted catalysis to attain covalent bonding to a carrier, were prepared. Optical microscopy and FTIR spectroscopy were used for the characterization of obtained materials. The films, with essential oil of Calendula officinalis L. and gallic acid, showed significantly increased percentage inhibition in DPPH• and ABTS•+ test (91% and 95%, respectively) after 10 minutes. The results, also, showed that all formulations of pectin biopolymer film, modified with gallic acid, can be successfully applied as a carrier for both types of ingredients.

In vitro evaluation of antioxidative activities of the extracts of petals of Paeonia lactiflora and Calendula officinalis incorporated in the new forms of biobased carriers

In this study, the petals collected from peony hybrid Paeonia lactiflora "Bowl of Beauty" and Calendula officinalis L. were extracted using an ethanol-water mixture assisted with microwave and ultrasonic treatment. The isolation of Calendula officinalis L. essential oil was done by hydrodistillation as well. The total phenolic and flavonoids content in the extracts and oil were determined and their antioxidant activity was evaluated. The highest total phenolic content was found for the extracts of hybrid P. lactiflora and C. officinalis L. obtained by ultrasound extraction (83.16 and 114.47 mg GA/g, respectively), while the flavonoid content obtained by microwave-assisted extraction was relatively high (123.48 and 65.29 mg QE/g, respectively). The highest antioxidant activity was obtained in DPPH• and ABTS•+ assay for the microwave-assisted extraction of hybrid P. lactiflora (79% and 83%) and ultrasound-assisted extraction of C. officinalis L. (45% and 49%), respectively. To improve antioxidant activity of both types of examined analytes (extracts and essential oil), the pectin biopolymer film (as a carrier) was prepared in the process of enzymatically assisted catalysis. Optical microscopy and FTIR spectroscopy were used for the characterization of obtained materials. The films, with essential oil of C. officinalis L. and gallic acid, showed significantly increased percentage inhibition in DPPH• and ABTS•+ test (91% and 95%, respectively) after 10 minutes. The results, also, showed that all formulations of pectin biopolymer film, modified with gallic acid, can be successfully applied as a carrier for both types of ingredients.

Antibacterial activities of medicinal plants used in Mexican traditional medicine

ETHNOPHARMACOLOGICAL RELEVANCE

We provide an extensive summary of the in vitro antibacterial properties of medicinal plants popularly used in Mexico to treat infections, and we discuss the ethnomedical information that has been published for these species.

MATERIALS AND METHODS

We carried out a bibliographic investigation by analyzing local and international peer-reviewed papers selected by consulting internationally accepted scientific databases from 1995 to 2014. We provide specific information about the evaluated plant parts, the type of extracts, the tested bacterial strains, and the inhibitory concentrations for each one of the species. We recorded the ethnomedical information for the active species, as well as their popular names and local distribution. Information about the plant compounds that has been identified is included in the manuscript. This review also incorporates an extensive summary of the available toxicological reports on the recorded species, as well as the worldwide registries of plant patents used for treating bacterial infections. In addition, we provide a list with the top plant species with antibacterial activities in this review RESULTS: We documented the in vitro antibacterial activities of 343 plant species pertaining to 92 botanical families against 72 bacterial species, focusing particularly on Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli and Pseudomonas aeruginosa. The plant families Asteraceae, Fabaceae, Lamiaceae and Euphorbiaceae included the largest number of active species. Information related to popular uses reveals that the majority of the plants, in addition to treating infections, are used to treat other conditions. The distribution of Mexican plants extended from those that were reported to grow in just one state to those that grow in all 32 Mexican states. From 75 plant species, 225 compounds were identified. Out of the total plant species, only 140 (40.57%) had at least one report about their toxic effects. From 1994 to July 2014 a total of 11,836 worldwide antibacterial patents prepared from different sources were recorded; only 36 antibacterial patents from plants were registered over the same time period. We offered some insights on the most important findings regarding the antibacterial effects, current state of the art, and research perspectives of top plant species with antibacterial activities in vitro.

CONCLUSIONS

Studies of the antibacterial in vitro activity of medicinal plants popularly used in Mexico to treat infections indicate that both the selection of plant material and the investigation methodologies vary. Standardized experimental procedures as well as in vivo pharmacokinetic studies to document the effectiveness of plant extracts and compounds are necessary. This review presents extensive information about the medicinal plants possessing antibacterial activity that has been scientifically studied and are popularly used in Mexico. We anticipate that this review will be of use for future studies because it constitutes a valuable information tool for selecting the most significant plants and their potential antibacterial properties.

The Protective Effect of Marigold Hydroalcoholic Extract in STZ-Induced Diabetic Rats: Evaluation of Cardiac and Pancreatic Biomarkers in the Serum

Diabetes mellitus is the most common endocrine disorder worldwide and it is usually along with complications such as retinopathy, neuropathy, nephropathy, and cardiovascular disease. The prevalence of diabetes is increasing and its treatment has created concerns in society. The use of herbal medicine can be helpful in the management of diabetes mellitus. The aim of this study was to investigate the protective effect of marigold hydroalcoholic extract under diabetes condition. A total of 36 male Wistar rats were randomly divided into four groups: normal control group, diabetic control group, and groups treated with 250 or 500 mg/kg hydroalcoholic extract of marigold flower during four weeks. At the end of the study, the rats were anesthetized with ketamine/xylazine, and sampling was performed through cardiac puncture. The results showed that treatment with marigold improved body weight. In addition, we determined that marigold normalized the level of CK-MB, total CK, amylase, and lipase in a dose-dependent manner. Probably these effects resulted from antioxidant property of marigold; thus we suggest that marigold flower can be useful for reduction of diabetes complication.

An enzoinformatics study targeting polo-like kinases-1 enzyme: Comparative assessment of anticancer potential of compounds isolated from leaves of Ageratum houstonianum

Natural products from plant sources, embracing inherently ample structural diversity than synthetic ones are the major sources of anticancer agents and will constantly play as protagonists for discovering new drugs. Polo-like kinases (PLKs) play a leading role in the ordered execution of mitotic events and 4 mammalian PLK family members have been identified. PLK1 is an attractive target for anticancer drugs in mammalian cells, among the four members of PLKs. The present study expresses the molecular interaction of compounds (1,2-Benzenedicarboxylic acid bis (2 ethylhexyl) ester, squalene, 3,5-bis (1,1-dimethylethyl) phenol, Pentamethyl tetrahydro-5H-chromene, (1,4-Cyclohexylphenyl) ethanone and 6-Vinyl-7-methoxy-2,2-dimethylchromene) isolated from methanolic extract of leaves of Ageratum houstonianum with PLK1 enzyme. Docking between PLK1 and each of these compounds (separately) was performed using “Auto dock 4.2.” (1,4-Cyclohexylphenyl) ethanone showed the maximum potential as a promising inhibitor of PLK1 enzyme with reference to ∆G (−6.84 kcal/mol) and Ki (9.77 μM) values. This was sequentially followed by Pentamethyl tetrahydro-5H-chromene (∆G = −6.60 kcal/mol; Ki = 14.58 μM), squalene (∆G = −6.17 kcal/mol; Ki = 30.12 μM), 6-Vinyl-7-methoxy-2,2-dimethylchromene (∆G = −5.91 kcal/mol; Ki = 46.68 μM), 3, 5-bis (1,1-dimethylethyl) phenol (∆G = −5.70 kcal/mol; Ki = 66.68 μM) and 1,2-Benzenedicarboxylic acid bis (2 ethylhexyl) ester (∆G = −5.58 kcal/mol; Ki = 80.80 μM). These results suggest that (1,4-Cyclohexylphenyl) ethanone might be a potent PLK1 inhibitor. Further, in vitro and in vivo rumination are warranted to validate the anticancer potential of (1,4-Cyclohexylphenyl) ethanone.

Review of current and "omics" methods for assessing the toxicity (genotoxicity, teratogenicity and nephrotoxicity) of herbal medicines and mushrooms

ETHNOPHARMACOLOGICAL RELEVANCE

The increasing use of traditional herbal medicines around the world requires more scientific evidence for their putative harmlessness. To this end, a plethora of methods exist, more or less satisfying. In this post-genome era, recent reviews are however scarce, not only on the use of new "omics" methods (transcriptomics, proteomics, metabonomics) for genotoxicity, teratogenicity, and nephrotoxicity assessment, but also on conventional ones.

METHODS

The present work aims (i) to review conventional methods used to assess genotoxicity, teratogenicity and nephrotoxicity of medicinal plants and mushrooms; (ii) to report recent progress in the use of "omics" technologies in this field; (iii) to underline advantages and limitations of promising methods; and lastly (iv) to suggest ways whereby the genotoxicity, teratogenicity, and nephrotoxicity assessment of traditional herbal medicines could be more predictive.

RESULTS

Literature and safety reports show that structural alerts, in silico and classical in vitro and in vivo predictive methods are often used. The current trend to develop "omics" technologies to assess genotoxicity, teratogenicity and nephrotoxicity is promising but most often relies on methods that are still not standardized and validated.

CONCLUSION

Hence, it is critical that toxicologists in industry, regulatory agencies and academic institutions develop a consensus, based on rigorous methods, about the reliability and interpretation of endpoints. It will also be important to regulate the integration of conventional methods for toxicity assessments with new "omics" technologies.

Antimicrobial activity of Calendula officinalis, Camellia sinensis and chlorhexidine against the adherence of microorganisms to sutures after extraction of unerupted third molars

Objective

The objective of this study was to compare the antimicrobial effect of mouthwashes containing Calendula officinalis L., Camellia sinensis (L.) Kuntze and 0.12% chlorhexidine digluconate on the adherence of microorganisms to suture materials after extraction of unerupted third molars.

Material and Methods

Eighteen patients with unerupted maxillary third molars indicated for extraction were selected (n=6 per mouthwash). First, the patients were subjected to extraction of the left tooth and instructed not to use any type of antiseptic solution at the site of surgery (control group). After 15 days, the right tooth was extracted and the patients were instructed to use the Calendula officinalis, Camellia sinensis or chlorhexidine mouthwash during 1 week (experimental group). For each surgery, the sutures were removed on postoperative day 7 and placed in sterile phosphate-buffered saline. Next, serial dilutions were prepared and seeded onto different culture media for the growth of the following microorganisms: blood agar for total microorganism growth; Mitis Salivarius bacitracin sucrose agar for mutans group streptococci; mannitol agar for Staphylococcus spp.; MacConkey agar for enterobacteria and Pseudomonas spp., and Sabouraud dextrose agar containing chloramphenicol for Candida spp. The plates were incubated during 24-48 h at 37ºC for microorganism count (CFU/mL).

Results

The three mouthwashes tested reduced the number of microorganisms adhered to the sutures compared to the control group. However, significant differences between the control and experimental groups were only observed for the mouthwash containing 0.12% chlorhexidine digluconate.

Conclusions

Calendula officinalis L. and Camellia sinensis (L.) Kuntze presented antimicrobial activity against the adherence of microorganisms to sutures but were not as efficient as chlorhexidine digluconate.

Effects of plant lectin and extracts on adhesion molecules of endothelial progenitors

Promise of cell therapy has advanced the use of adult stem cells towards the development of novel approaches to promote regeneration of injured endothelium. The aim of this study was to stimulate endothelial progenitor cells (EPCs) with lectin isolated from Solanum tuberosum (potato) shoot and Calendula officinalis (marigold) extracts, in order to increase EPCs proliferation and gene expression of molecules with roles in chemotaxis and adhesion for a better attachment to injured vascular tissue. EPCs were differentiated from umbilical cord blood-derived mononuclear cells and characterized by light microscopy, flow cytometry, and vascular tube-like structures formation on Matrigel. Cell proliferation was determined by MTS assay, and gene expression of molecules involved in EPCs adhesion (VCAM-1, VE-cadherin, ICAM-1, PECAM-1, P-selectin) and chemotaxis was determined (CXCR4, Tie-2) by RT-PCR. For the assessment of cell motility, wound-healing assay was employed. Both potato shoot lectin and marigold extracts stimulated EPCs proliferation in a concentration dependent manner and were able to increase expression of adhesion and chemotactic molecules. Marigold flower extract proved to be more efficient. This study demonstrates the usefulness of potato lectin and marigold extracts to increase EPCs proliferation and modulate gene expression of chemotactic and adhesion molecules, which may facilitate EPCs attachment to injured endothelium.

Final Report of the Cosmetic Ingredient Review Expert Panel Amended Safety Assessment of Calendula officinalis—Derived Cosmetic Ingredients

Calendula officinalis extract, C officinalis flower, C officinalis flower extract, C officinalis flower oil, and C officinalis seed oil are cosmetic ingredients derived from C officinalis. These ingredients may contain minerals, carbohydrates, lipids, phenolic acids, flavonoids, tannins, coumarins, sterols and steroids, monoterpenes, sesquiterpenes, triterpenes, tocopherols, quinones, amino acids, and resins. These ingredients were not significantly toxic in single-dose oral studies using animals. The absence of reproductive/developmental toxicity was inferred from repeat-dose studies of coriander oil, with a similar composition. Overall, these ingredients were not genotoxic. They also were not irritating, sensitizing, or photosensitizing in animal or clinical tests but may be mild ocular irritants. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that these ingredients are safe for use in cosmetics in the practices of use and concentration given in this amended safety assessment.

Antifungal activity of the essential oil from Calendula officinalis L. (asteraceae) growing in Brazil

This study tested in vitro activity of the essential oil from flowers of Calendula officinalis using disk-diffusion techniques. The antifungal assay results showed for the first time that the essential oil has good potential antifungal activity: it was effective against all 23 clinical fungi strains tested.

Assessment of the mutagenic, antimutagenic and cytotoxic activities of ethanolic extract of araticum (Annona crassiflora Mart. 1841) by micronucleus test in mice

A typical Brazilian plant, araticum (Annona crassiflora Mart.), is widely used in humans as therapeutic medicine to treat several diseases such as diarrhea, rheumatism and syphilis. It contains acetogenins which present cytotoxic, antitumogenic, and antiparasitic properties. In this study, mutagenic, antimutagenic and cytotoxic effects of araticum leaves ethanolic extract were evaluated by micronucleus test in mice. To evaluate the mutagenic activity, animals were treated with ethanolic extract of araticum (EEA) using 10, 20, 50, 100 and 160 mg.kg-1. For all doses, micronucleated polychromatic erythrocytes (MNPCE) frequency was evaluated at 24, 48 and 72 hours after treatment. To evaluate the antimutagenic activity, animals were treated with 10, 20, 50 and 100 mg.kg-1 of EEA and 4 mg.kg-1 of MMC simultaneously. The frequency of MNPCE was evaluated 36 hours after exposure. Cytotoxicity was evaluated by the polychromatic and normochromatic erythrocytes ratio (PCE/NCE). In the mutagenicity assessment, all doses of EEA resulted in no significant increase of MNPCE (P > 0.05), compared to solvent- control group. Regarding administration time, no significant difference among three evaluation periods was observed (P > 0.05). Such results indicate that EEA did not exert mutagenic activity. Cytotoxicity was evident in doses of 50, 100 and 160 mg.kg-1 at 24 and 48 hours after exposure. Concerning antimutagenicity, except the 10 mg.kg-1 co-administered with 4 mg/kg of MMC, all doses reduced significantly the frequency of MNPCE compared to the positive control group (P < 0.05). These results, therefore, indicate an antimutagenic activity of the EEA. Cytotoxicity was significantly increased (P < 0.01) at 100 mg.kg-1 EEA doses co-administered with 4 mg.kg-1 of MMC.

Toxicological studies on hydroalcohol extract of Calendula officinalis L

The hydroalcohol extract (HAE) of Calendula officinalis L. was evaluated for its acute toxicity by the oral route in rats and mice and for the subacute effect on hematological, biochemical and morphologic parameters in rats. In the acute toxicity test, HAE failed to cause death in the animals after administration of oral doses up to 5.0 g/kg. Oral treatment with HAE at 0.025, 0.25, 0.5 and 1.0 g/kg did not induce hematological alterations when compared with the control group. In the biochemical parameters, there was an increase in blood urea nitrogen (BUN) and in alanine transaminase (ALT) levels. Morphological examination of the brain, kidney and heart did not show any alteration. However, inflammatory sites were found in the lung and liver, which were associated, respectively, with oral gavage and a possible hepatotoxic effect. HAE was non-toxic in rats, although there was evidence of renal and liver overload.

Marigold (Calendula officinalis L.): an evidence-based systematic review by the Natural Standard Research Collaboration

An evidence-based systematic review including written and statistical analysis of scientific literature, expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology and dosing.

Genotoxic and anti-genotoxic properties of Calendula officinalis extracts in rat liver cell cultures treated with diethylnitrosamine

Calendula officinalis flower extracts are used to cure inflammatory and infectious diseases, for wound healing and even cancer with partial objective evidence of its therapeutic properties or toxic effects, many of which can be attributed to the presence of flavonols. We studied whether C. officinalis extracts induce unscheduled DNA synthesis (UDS) in rat liver cell cultures, and if these extracts can reverse diethylnitrosamine (DEN)-induced UDS. Four different flower extracts were prepared: aqueous (AE), aqueous-ethanol (AEE), ethanol (EE) and chloroform (CE). AE and AEE were evaporated to 6.72 and 4.54 mg of solid material per ml, respectively and final ethanol concentration in AEE was 0.8%. EE and CE were dried and resuspended in dimethyl sulfoxide (DMSO) to 19.2 and 10 mg of solid material per ml. Ethanol residue of EE was 0.34%. In the UDS assay in liver cell cultures, DEN at 1.25 microM produced a maximal increase of 40% (3)H-thymidine ((3)HdTT) incorporation, and both, AE and AEE showed complete reversion of the DEN effect at around 50 ng/ml and between 0.4 to 16 ng/ml, respectively. In the absence of DEN, these two polar extracts induced UDS at concentrations of 25 microg for AE and 3.7 microg/ml for AEE to 100 microg/ml in rat liver cell cultures. Concentrations producing genotoxic damage were three orders of magnitude above concentrations that conferred total protection against the DEN effect. Thus, at the lower end, ng/ml concentrations of the two polar extracts AE and AEE conferred total protection against the DEN effect and at the higher end, g/ml concentrations produced genotoxic effects. These results justify the study of C. officinalis flower extracts to obtain products with biological activity and to define their genotoxic or chemopreventive properties.

Evaluation of the immunomodulatory effects of five herbal plants

A group of medicinal plants including, Silybum marianum, Matricaria chamomilla, Calendula officinalis, Cichorium intybus and Dracocephalum kotschyi which grow in Iran, were extracted with ethanol 70% and the mitogenic activity was examined both on human peripheral blood lymphocytes and thymocytes. Effect of these extracts on proliferative responsiveness of human lymphocytes to phytohemagglutinin (PHA) and on the mixed lymphocyte reaction (MLR) was also investigated. The results obtained indicated that none of the extracts had a direct mitogenic effect on human lymphocytes or thymocytes (stimulation index, SI<0.07). Among the plants studied, C. intybus and C. officinalis showed a complete inhibitory effect on the proliferation of lymphocytes in the presence of PHA (SI range 0.01-0.49). A dose dependent inhibitory effect was obtained in the case of D. kotschyi. Extract of M. chamomilla showed almost no stimulatory effect. A significant decrease in proliferation assay due to 0.1-10 microg/ml of S. marianum was observed (SI<0.46, P<0.05). In MLR, a markedly stimulatory effect with some lower concentrations of all the extracts except Dracocephalum was detected. The highest stimulatory effect was due to 100 microg/ml of S. marianum (SI 2.82). Treatment of mixed lymphocytes with 0.1-10 microg/ml of C. officinalis (SI range 1.34-1.80) and 10 microg/ml of M. chamomilla and C. intybus (SI 2.18 and 1.70, respectively) strongly increased the cell proliferation. In conclusion, this in vitro study revealed the capacity of all the extracts except Dracocephalum to enhance the proliferation of lymphocytes after stimulation with the allogenic cells.