Heikki Vuorela

Antimicrobial effects of Finnish plant extracts containing flavonoids and other phenolic compounds

Plant phenolics, especially dietary flavonoids, are currently of growing interest owing to their supposed functional properties in promoting human health. Antimicrobial screening of 13 phenolic substances and 29 extracts prepared from Finnish plant materials against selected microbes was conducted in this study. The tests were carried out using diffusion methods with four to nine microbial species (Aspergillus niger, Bacillus subtilis, Candida albicans, Escherichia coli, Micrococcus luteus, Pseudomonas aeruginosa, Saccharomyces cerevisiae, Staphylococcus aureus and Staphylococcus epidermidis). Flavone, quercetin and naringenin were effective in inhibiting the growth of the organisms. The most active plant extracts were purple loosestrife (Lythrum salicaria L.) against Candida albicans, meadowsweet (Filipendula ulmaria (L.) Maxim.), willow herb (Epilobium angustifolium L.), cloudberry (Rubus chamaemorus L.) and raspberry (Rubus idaeus L.) against bacteria, and white birch (Betula pubescens Ehrh.), pine (Pinus sylvestris L.) and potato (Solanum tuberosum. L.) against gram-positive Staphylococcus aureus.

What made sesquiterpene lactones reach cancer clinical trials

Sesquiterpene lactones (SLs) are plant-derived compounds often used in traditional medicine against inflammation and cancer. This review focuses on the chemical and biological properties of SLs that lead to enhanced anticancer and anti-inflammatory effects. The chemical properties comprise alkylating center reactivity, lipophilicity, and molecular geometry and electronic features. SLs in clinical trials are artemisinin, thapsigargin and parthenolide and many of their synthetic derivatives. These drugs are selective toward tumor and cancer stem cells by targeting specific signaling pathways, which make them lead compounds in cancer clinical trials.

Antimicrobial activity of some coumarin containing herbal plants growing in Finland.

Antimicrobial screening against selected Gram-positive and Gram-negative bacteria, yeasts, mold, as well as plant pathogenic fungi, with emphasis on method optimization was carried out on methanol extracts prepared from seven plants grown in Finland. Sensitivity to the extracts was found to vary considerably among the micro-organisms, the extract from Petroselinum crispum and Ruta graveolens showing the highest toxicity against Rhizoctonia solani. The growth of Heterobasidium annosum was inhibited, whereas that of Phytophtora (cactorum) was promoted by all the extracts. The antibacterial and antifungal activities of six natural coumarin compounds were weak, except for the inhibitory effect against Fusarium culmorum.

Reactive oxygen species mediate thymoquinone-induced apoptosis and activate ERK and JNK signaling.

Thymoquinone (TQ), a component of black seed essential oil, is known to induce apoptotic cell death and oxidative stress, however, the direct involvement of oxidants in TQ-induced cell death has not been established yet. Here, we show that TQ inhibited the proliferation of a panel of human colon cancer cells (Caco-2, HCT-116, LoVo, DLD-1 and HT-29), without exhibiting cytotoxicity to normal human intestinal FHs74Int cells. Further investigation in DLD-1 revealed that apoptotic cell death is the mechanism for TQ-induced growth inhibition as confirmed by flow cytometry, M30 cytodeath and caspase-3/7 activation. Apoptosis was induced via the generation of reactive oxygen species (ROS) as evidenced by the abrogation of TQ apoptotic effect in cells preincubated with the strong antioxidant N-acetyl cysteine (NAC). TQ increased the phosphorylation states of the mitogen-activated protein kinases (MAPK) JNK and ERK, but not of p38. Their activation was completely abolished in the presence of NAC. Using PD98059 and SP600125, specific ERK and JNK inhibitors, the two kinases were found to possess pro-survival activities in TQ-induced cell death. These data present evidence linking the pro-oxidant effects of TQ with its apoptotic effects in colon cancer and prove a protective role of MAPK.

Ethnobotanical and antimicrobial investigation on some species of Terminalia and Combretum (Combretaceae) growing in Tanzania

An ethnobotanical investigation on the medicinal uses of some species of Terminalia and Combretum (Combretaceae) was carried out in Mbeya, Tanzania during a 5-weeks field expedition. Of the sixteen species collected, Combretum fragrans F. Hoffm., Combretum molle G. Don., Combretum psidioides Welw., Combretum zeyheri Sond., Terminalia kaiserana F. Hoffm. and Terminalia sericea Burch ex. DC. have medical applications against various bacterial infections, such as gonorrhoea and syphilis, and against symptoms like diarrhoea, hypertension and even cancer. Antimicrobial screening of the crude extracts of the selected Combretum and Terminalia species was performed by the agar diffusion method. Among the most effective extracts were methanol extracts of the roots of Terminalia sambesiaca Engl. & Diels., T. kaiserana Guill. & Perrott., T. sericea Burch. ex DC., C. fragrans F. Hoffm. and Combretum padoides Engl. & Diels., all of which showed marked inhibition against Gram-positive bacteria, and were also good inhibitors of Enterobacter aerogenes. All four of the extracts of the roots of T. sericea tested, (methanol, ethanol, acetone and hot water) had good antimicrobial activity. A methanolic leaf extract of T. kaiserana was the only extract to have a bacteriocidic effect on Escherichia coli. Methanol root extracts of T. sambesiaca and methanol leaf extracts of T. sericea were the most effective against Candida albicans. The results of the antimicrobial screening support the ethnomedical uses of these plants.

PN 200-110, a new calcium antagonist: electrophysiological, inotropic, and chronotropic effects on guinea pig myocardial tissue and effects on contraction and calcium uptake of rabbit aorta

The compound isopropyl 4-(2,1,3-benzoxadiazol-4-yl) - 1,4-dihydro-5-methoxycarbonyl-2.6-dimethyl-3-pyridinecarboxylate (code name PN 200–110 [PN]) was investigated for calcium antagonistic effects in experiments in vitro. Action potentials recorded with intracellular microelectrodes in guinea pig papillary muscles were changed little by PN, 10-7 M, except for a slight shortening of the duration of the plateau phase. Slow action potentials elicited in partially depolarized papillary muscles were gradually diminished and finally blocked by this concentration of PN. Contractile force was diminished in normal and partially depolarized muscles. The rate of spontaneously beating guinea pig right atria was decreased dose dependently, and the EC25 was 4.5 × 10-10 M. The EC25 for the negative inotropic effects measured on paced guinea pig left atria was 1.5 × 10-8 M. No membrane-stabilizing effects were found. Calcium-induced contraction of rabbit aorta in depolarizing bath solution was inhibited with an apparent pA2 of 10.3. Contraction elicited by graded depolarization at a constant calcium concentration was inhibited with an EC50 of 1.4 × 10-9 M. Under resting conditions PN did not alter net uptake of 45Ca2+. KCl-stimulated uptake was inhibited with an EC50 of 3.6 × 10-9 M. Neither noradrenaline-induced contractions nor noradrenaline-stimulated net uptake of 45Ca2+ were inhibited by a concentration of PN as high as 10 -5 M. PN thus is selective on cardiac tissue with respect to negative chronotropic versus inotropic activity and on rabbit aorta with respect to potential-operated versus receptor-operated channels.

Differential inhibition of coumarin 7-hydroxylase activity in mouse and human liver microsomes

Coumarin is 7-hydroxylated by the P450 isoform Cyp2a-5 in mice and CYP2A6 in humans. Various drugs, endogenous substances, plant substances and carcinogens, altogether about 90 chemicals, were evaluated as possible inhibitors of coumarin 7-hydroxylase (COH) activity in mouse microsomes. The effects of selected compounds on COH activity in human liver microsomes were also tested. The furanocoumarin derivatives methoxsalen (8-methoxypsoralen) and psoralen proved to be the most potent inhibitors of mouse COH activity (IC50 values 1.0 and 3.1 microM, respectively). The furanocoumarins bergapten (5-methoxypsoralen), isopimpinellin (5,8-dimethoxypsoralen), imperatorin and sphondin also effectively inhibited mouse COH activity (IC50 values 19-40 microM). Methoxsalen, isopimpinellin and metyrapone were also inhibitors in mice in vivo. Methoxsalen was a potent inhibitor of COH activity also in human liver microsomes, (IC50 value 5.4 microM), whereas bergapten, isopimpinellin and imperatorin had no effect. The imidazole antimycotic miconazole was a potent but non-specific inhibitor of COH activity. Several known substrates and inhibitors of members in the CYP1A, CYP2B, CYP2C, CYP2D and CYP3A subfamilies were poor inhibitors of COH activity. These results suggest that (i) the coumarin-type compounds in particular interact with the active sites of Cyp2a-5 and CYP2A6, and (ii) the active sites of Cyp2a-5 and CYP2A6 are structurally different, since a number of compounds inhibited mouse, but not human COH activity.

Bioactivity of certain Egyptian Ficus species

The fruit extracts of Ficus sycomorus L., F. benjamina L., F. bengalensis L. and F. religiosa L. were screened for bioactivity. F. bengalensis and F. religiosa demonstrated activity in the brine shrimp test (Artemia salina) which indicates toxicity, whereas F. sycomorus and F. benjamina showed no activity. All the fruit extracts exhibited antitumor activity in the potato disc bioassay. None of the tested extracts showed any marked inhibition on the uptake of calcium into rat pituitary cells GH4C1. The extracts of the four tested Ficus species had significant antibacterial activity, but no antifungal activity. The results of this preliminary investigation support the traditional use of these plants in folk medicine for respiratory disorders and certain skin diseases.

High-performance liquid chromatographic determination of oligomeric procyanidins from dimers up to the hexamer in hawthorn

An HPLC method using UV diode array detection was developed for analysing procyanidins qualitatively and quantitatively up to the hexameric level in hawthorn samples. The analysed compounds included procyanidin dimers B-2, B-4 and B-5, procyanidin trimers C-1, epicatechin-(4beta-->8)-epicatechin-(4beta-->6)-epicatechin and epicatechin-(4beta-->6)-epicatechin-(4beta-->8)-epicatechin, a tetramer D-1 and a pentamer E-1 both consisting of (-)-epicatechin units linked through C-4beta/C-8 bonds. The concentrations of two unknown tetramers and a hexamer F were also quantified. The oligomeric procyanidins (OPs) were specifically determined due to the development of a method for isolating them from hawthorn during sample preparation. The pattern of oligomeric procyanidins in the leaves, flowers and fruits was similar, but the concentrations varied depending on the part of the plant. The concentration in leaves was 1.6%, in flowers 1.2% and in fruits 0.2% of the dry mass. The method was validated with respect to repeatability, recovery, linearity, and sensitivity. The repeatability for the quantitative analytical method of all the OPs in leaves was 7.7%, in flowers 8.8%, and in fruits 12.3%. The recovery of the main OPs ranged from 91 to 97%. The correlation coefficients of calibration curves were between 0.997 and 1.000. The limits of quantitation for different procyanidin standards were 0.05-0.12 mg/ml, when 10 microl of each standard solution was injected into the HPLC.

Exploring Marine Resources for Bioactive Compounds

Biodiversity in the seas is only partly explored, although marine organisms are excellent sources for many industrial products. Through close co-operation between industrial and academic partners, it is possible to successfully collect, isolate and classify marine organisms, such as bacteria, fungi, micro- and macroalgae, cyanobacteria, and marine invertebrates from the oceans and seas globally. Extracts and purified compounds of these organisms can be studied for several therapeutically and industrially significant biological activities, including anticancer, anti-inflammatory, antiviral, antibacterial, and anticoagulant activities by applying a wide variety of screening tools, as well as for ion channel/receptor modulation and plant growth regulation. Chromatographic isolation of bioactive compounds will be followed by structural determination. Sustainable cultivation methods for promising organisms and biotechnological processes for selected compounds can be developed, as well as biosensors for monitoring the target compounds. The (semi)synthetic modification of marine-based bioactive compounds produces their new derivatives, structural analogs and mimetics that could serve as hit or lead compounds and be used to expand compound libraries based on marine natural products. The research innovations can be targeted for industrial product development in order to improve the growth and productivity of marine biotechnology. Marine research aims at a better understanding of environmentally conscious sourcing of marine biotechnology products and increased public awareness of marine biodiversity. Marine research is expected to offer novel marine-based lead compounds for industries and strengthen their product portfolios related to pharmaceutical, nutraceutical, cosmetic, agrochemical, food processing, material and biosensor applications.