Tannin-rich Extract Research Articles

Inhibition of Pancreatic Lipase and Triacylglycerol Intestinal Absorption by a Pinhão Coat (Araucaria angustifolia) Extract Rich in Condensed Tannin.

The purpose of the present work was to characterize the possible inhibition of pancreatic lipase by a tannin-rich extract obtained from the pinhão (Araucaria angustifolia seed) coat, based on the previous observation that this preparation inhibits α-amylases. Kinetic measurements of pancreatic lipase revealed that the pinhão coat tannin is an effective inhibitor. Inhibition was of the parabolic non-competitive type. The inhibition constants, and , were equal to 332.7 ± 146.1 μg/mL and 321.2 ± 93.0 μg/mL, respectively, corresponding roughly to the inhibitor concentration producing 50% inhibition ([I]50). Consistently, the pinhão coat extract was also effective at diminishing the plasma triglyceride levels in mice after an olive oil load; 50% diminution of the area under the plasma concentration versus the time curve occurred at a dose of 250 mg/kg. This observation is most probably the consequence of an indirect inhibition of triglyceride absorption via inhibition of pancreatic lipase. For the pinhão coat tannin, this is the second report of a biological activity, the first one being a similar inhibition of the absorption of glucose derived from starch as a consequence of an inhibitory action on α-amylases. Taken together, these effects represent a potential anti-obesity action, as suggested for other polyphenol or tannin-rich preparations.

Antioxidative activity of the polyphenols from the involucres of Castanea mollissima Blume and their mitigating effects on heat stress

Polyphenols extracted from plants have multiple functions in animal production. To explore new sources of tannin-rich extracts, which have potential benefits for animal health, this study focused on the effects of polyphenolic extracts from involucres of Castanea mollissima Blume (PICB) on heat-stressed broilers. In vitro experiments were first performed using intestinal cryptlike epithelial cell line-6 (IEC-6) cells to evaluate the effects of PICB on cell proliferation and antioxidative parameters under normal and heat-stress conditions. Then in vivo experiments were carried out with 2 trials: in trial 1, 400 one-d-old male Arbor Acres (AA) broilers were randomly assigned to 5 groups (4 replicates/group, 20 chicks/replicate): group 1 was a normal control group fed the basic ration; groups 2 to 5 were fed the basic ration supplemented with 0.2% vitamin C and 0.2%, 0.3%, and 0.4% PICB, respectively. Trial 1 lasted 42 d, and growth performance was monitored every week. At the end of the trial, the chicks were sacrificed and sampled. In trial 2, 400 twenty-eight-d-old chicks were randomly assigned to 5 groups as described in trial 1. After 1 week of adaptation, heat stress was applied for 7 consecutive days. On days 3 and 7 of heat stress, the chicks were sacrificed and sampled. The results showed that PICB could stimulate IEC-6 cell proliferation and had strong in vitro antioxidant activity. PICB had no effect on the growth performance and carcass parameters of AA broilers in trial 1, whereas in trial 2, group 4 saw improved growth performance and antioxidant activity compared to the first three groups (P < 0.05). In conclusion, PICB had no effects on the growth performance of IEC-6 cells and AA broilers under normal conditions, whereas it could mitigate heat-stress effects on the growth performance and antioxidant activity of IEC-6 cells and AA broilers, implying that PICB could be used as a suitable additive to improve animal production under heat-stress conditions.

Hydrolysable tannin fed to entire male pigs affects intestinal production, tissue deposition and hepatic clearance of skatole

The effect of adding hydrolysable tannins to the diet of fattening boars was studied. Performance, reproductive organ weights, salivary gland morphology, boar taint compounds and skatole metabolism were evaluated. At 123 days of age and 52 ± 6 kg liveweight, 24 Landrace × Large White boars were assigned within a litter to four treatment groups: control (T0 fed mixture with 13.2 MJ/kg, 17.5% crude proteins) and three experimental diets for which the T0 diet was supplemented with 1%, 2% and 3% of hydrolysable tannin-rich extract (T1, T2 and T3, respectively). Pigs were kept individually with ad libitum access to feed and water and slaughtered at 193 days of age and 122 ± 10 kg liveweight.Adding hydrolysable tannins to the diet had no negative effect on growth performance at 1% and 2%, whereas the 3% inclusion reduced feed intake and resulted in an adaptive response of the salivary glands (particularly parotid gland hypertrophy). Relative to T0, fat tissue skatole concentration was increased in the T1 group, but was similar in T2 and T3. Across treatments tissue skatole concentrations were proportional to the activity of hepatic CYP450. The results indicate the potential of tannin supplementation to reduce boar taint although further investigations are needed in order to establishing optimal dosage.

Sustained release of a purified tannin component of Terminalia chebula from a titanium implant surface prevents biofilm formation by Staphylococcus aureus.

Although biofilms are formed on a variety of surfaces, of utmost significance are those formed on prosthetic devices used as implants. Such biofilms can lead to severe device-related infections that are difficult to treat. In a search for new antibiofilm agents that can be used as "active" implant coatings, purified fraction from a tannin-rich extract of Terminalia chebula was isolated and tested for its antibiofilm properties on a titanium implant material. The fraction, named as Fraction 7, was found to significantly reduce biofilm formation by hospital isolates of Staphylococcus aureus, at sub-inhibitory concentrations that were 64 times lower than the minimum inhibitory concentration (MIC). Simulated local delivery systems of the Fraction 7 set upon the surface of titanium alloy released the fraction in a controlled manner from a biodegradable carrier (PDLLA) and were found to significantly reduce biofilm formation by a methicillin-resistant hospital isolate of S. aureus in a load concentration dependent manner without preventing growth. This study therefore identifies a novel fraction from tannin-rich extract of T. chebula that has potential to be used as an antibiofilm coat on implant surfaces.

Tannins from Hamamelis virginiana Bark Extract: Characterization and Improvement of the Antiviral Efficacy against Influenza A Virus and Human Papillomavirus

Antiviral activity has been demonstrated for different tannin-rich plant extracts. Since tannins of different classes and molecular weights are often found together in plant extracts and may differ in their antiviral activity, we have compared the effect against influenza A virus (IAV) of Hamamelis virginiana L. bark extract, fractions enriched in tannins of different molecular weights and individual tannins of defined structures, including pseudotannins. We demonstrate antiviral activity of the bark extract against different IAV strains, including the recently emerged H7N9, and show for the first time that a tannin-rich extract inhibits human papillomavirus (HPV) type 16 infection. As the best performing antiviral candidate, we identified a highly potent fraction against both IAV and HPV, enriched in high molecular weight condensed tannins by ultrafiltration, a simple, reproducible and easily upscalable method. This ultrafiltration concentrate and the bark extract inhibited early and, to a minor extent, later steps in the IAV life cycle and tannin-dependently inhibited HPV attachment. We observed interesting mechanistic differences between tannin structures: High molecular weight tannin containing extracts and tannic acid (1702 g/mol) inhibited both IAV receptor binding and neuraminidase activity. In contrast, low molecular weight compounds (<500 g/mol) such as gallic acid, epigallocatechin gallate or hamamelitannin inhibited neuraminidase but not hemagglutination. Average molecular weight of the compounds seemed to positively correlate with receptor binding (but not neuraminidase) inhibition. In general, neuraminidase inhibition seemed to contribute little to the antiviral activity. Importantly, antiviral use of the ultrafiltration fraction enriched in high molecular weight condensed tannins and, to a lesser extent, the unfractionated bark extract was preferable over individual isolated compounds. These results are of interest for developing and improving plant-based antivirals.

Composition and Biological Activities of Hydrolyzable Tannins of Fruits of Phyllanthus emblica

Fruits of emblic leafflower have been used as food and traditional medicine in Asia. A wide range of biological activities have been shown in modern research suggesting potential of the fruits as healthy food and raw material for bioactive ingredients of food. Hydrolyzable tannins are among the major bioactive components of the fruits. Mucic acid gallate, mucic acid lactone gallate, monogalloylglucose, gallic acid, digalloylglucose, putranjivain A, galloyl-HHDP-glucose, elaeocarpusin, and chebulagic acid are the most abundant hydrolyzable tannins. The compositional profiles of tannins in the fruits vary depending on the cultivars as well as ripening stages. Fruits and tannin-rich extracts of fruits have shown antidiabetic, antimicrobial, anti-inflammatory, and immune-regulating activities in vitro and in animal studies. The fruits and fruit extracts have manifested protective effects on organs/tissues from damages induced by chemicals, stresses, and aging in animal models. The fruits and fruit extracts have potential in inhibiting the growth of cancer cells and reducing DNA damage induced by chemicals and radiation. Antioxidative activities are likely among the mechanisms of the biological activities and physiological effects. Human intervention/clinical studies are needed to investigate the bioavailability and metabolism of the tannins and to substantiate the health benefits in humans. Emblic leafflower may be a potential raw material for natural food preservatives.

Effects of long-term supplementation of chestnut and valonea extracts on methane release, digestibility and nitrogen excretion in sheep

The long-term effects of adding chestnut (CHE; Castanea sativa) and valonea (VAL; Quercus valonea) tannin-rich extracts to sheep feed were investigated. In Experiment 1, sheep (65 kg BW) were fed 842 g/day of a ryegrass-based hay. The control-treated animals (CON) received 464 g/day of concentrate, and tannin-treated animals received the same amount of concentrate additionally containing 20 g of the respective tannin-rich extract. Hay and concentrates were offered together in one meal. After the onset of treatment, methane release was measured in respiration chambers for 23.5-h intervals (nine times) in a 190-days period. Faeces and urine were collected three times (including once before the onset of the tannin treatment) to assess digestibility and urinary excretion of purine derivatives. Based on the results obtained from Experiment 1, a second experiment (Experiment 2) was initiated, in which the daily tannin dosage was almost doubled (from 0.9 (Experiment 1) to 1.7 g/kg BW0.75). With the exception of the dosage and duration of the treatment (85 days), Experiment 2 followed the same design as Experiment 1, with the same measurements. In an attempt to compare in vitro and in vivo effects of tannin supplementation, the same substrates and tannin treatments were examined in the Hohenheim gas test. In vitro methane production was not significantly different between treatments. None of the tannin-rich extract doses induced a reduction in methane in the sheep experiments. On the 1st day of tannin feeding in both experiments, tannin inclusion tended to decrease methane release, but this trend disappeared by day 14 in both experiments. In balance period 3 of Experiment 1, lower dry matter and organic matter digestibility was noted for tannin treatments. The digestibility of CP, but not NDF or ADF, was reduced in both experiments. A significant shift in N excretion from urine to faeces was observed for both tannin-rich extracts in both experiments, particularly in Experiment 2. In balance period 2 of Experiment 2, an increased intake of metabolisable energy for VAL was observed. The urinary excretion of purine derivatives was not significantly different between treatments, indicating that microbial protein synthesis was equal for all treatments. Thus, we concluded that both tannin-rich extracts temporary affect processes in the rumen but did not alter methane release over a longer period.

Effects of different tannin-rich extracts and rapeseed tannin monomers on methane formation and microbial protein synthesis in vitro

Tannins, polyphenolic compounds found in plants, are known to complex with proteins of feed and rumen bacteria. This group of substances has the potential to reduce methane production either with or without negative effects on digestibility and microbial yield. In the first step of this study, 10 tannin-rich extracts from chestnut, mimosa, myrabolan, quebracho, sumach, tara, valonea, oak, cocoa and grape seed, and four rapeseed tannin monomers (pelargonidin, catechin, cyanidin and sinapinic acid) were used in a series of in vitro trials using the Hohenheim gas test, with grass silage as substrate. The objective was to screen the potential of various tannin-rich extracts to reduce methane production without a significant effect on total gas production (GP). Supplementation with pelargonidin and cyanidin did not reduce methane production; however, catechin and sinapinic acid reduced methane production without altering GP. All tannin-rich extracts, except for tara extract, significantly reduced methane production by 8% to 28% without altering GP. On the basis of these results, five tannin-rich extracts were selected and further investigated in a second step using a Rusitec system. Each tannin-rich extract (1.5 g) was supplemented to grass silage (15 g). In this experiment, nutrient degradation, microbial protein synthesis and volatile fatty acid production were used as additional response criteria. Chestnut extract caused the greatest reduction in methane production followed by valonea, grape seed and sumach, whereas myrabolan extract did not reduce methane production. Whereas chestnut extract reduced acetate production by 19%, supplementation with grape seed or myrabolan extract increased acetate production. However, degradation of fibre fractions was reduced in all tannin treatments. Degradation of dry matter and organic matter was also reduced by tannin supplementation, and no differences were found between the tannin-rich extracts. CP degradation and ammonia-N accumulation in the Rusitec were reduced by tannin treatment. The amount and efficiency of microbial protein synthesis were not significantly affected by tannin supplementation. The results of this study indicated that some tannin-rich extracts are able to reduce methane production without altering microbial protein synthesis. We hypothesized that chestnut and valonea extract have the greatest potential to reduce methane production without negative side effects.

Bactericidal effect of hydrolysable and condensed tannin extracts on Campylobacter jejuni in vitro

Strategies are sought to reduce intestinal colonisation of food-producing animals by Campylobacter jejuni, a leading bacterial cause of human foodborne illness worldwide. Presently, we tested the antimicrobial activity of hydrolysable-rich blackberry, cranberry and chestnut tannin extracts and condensed tannin-rich mimosa, quebracho and sorghum tannins (each at 100mg/mL) against C. jejuni via disc diffusion assay in the presence of supplemental casamino acids. We found that when compared to non-tannin-treated controls, all tested tannins inhibited the growth of C. jejuni and that inhibition by the condensed tannin-rich mimosa and quebracho extracts was mitigated in nutrient-limited medium supplemented with casamino acids. When tested in broth culture, both chestnut and mimosa extracts inhibited growth of C. jejuni and this inhibition was much greater in nutrient-limited than in full-strength medium. Consistent with observations from the disc diffusion assay, the inhibitory activity of the condensed tannin-rich mimosa extracts but not the hydrolysable tannin-rich chestnut extracts was mitigated by casamino acid supplementation to the nutrient-limited medium, likely because the added amino acids saturated the binding potential of the condensed tannins. These results demonstrate the antimicrobial activity of various hydrolysable and condensed tannin-rich extracts against C. jejuni and reveal that condensed tannins may be less efficient than hydrolysable tannins in controlling C. jejuni in gut environments containing high concentrations of amino acids and soluble proteins.

Comparing the sensitivity of two in vitro assays to evaluate the anthelmintic activity of tropical tannin rich plant extracts against Haemonchus contortus

The present trial aimed at comparing the sensitivity of two in vitro methods, i.e. the larval migration inhibition assay (LMIA) and the larval exsheathment inhibition assay (LEIA), to evaluate the anthelmintic (AH) properties of tannin-rich plant extracts against Haemonchus contortus infective larvae. The two assays were applied on the same batch of H. contortus infective larvae exposed to water/acetonic extracts obtained from four tropical plants with different tannin contents: Acacia gaumeri, Brosimum alicastrum, Havardia albicans and Leucaena leucocephala. Increasing concentrations (0, 75, 150, 300, 600, 1200μg/ml PBS) of lyophilized extracts were used in both in vitro assays. A general lineal model test was used to determine the dose-effect in the LMIA or the difference in the percentage of exsheathed larvae between the respective control and treated groups. The LMIA showed a dose-dependent AH effect for H. albicans (P<0.001) and A. gaumeri (P<0.05), but not for L. leucocephala and B. alicastrum. In contrast, the exsheathment process was significantly affected by all doses of H. albicans and A. gaumeri extracts and a significant dose-dependent effect was found for B. alicastrum and L. leucocephala. Calculation of lethal dose (LD) was possible with LEIA using B. alicastrum and L. leucocephala but not with H. albicans and A. gaumeri as the lowest tested concentration was achieving more than 50% inhibition. Calculation of LD with the LMIA results was not feasible. These results suggest that tannin-rich plant extracts are more potent inhibitors of the exsheathment of H. contortus L3 larvae than their motility. This information underlines the difference of sensitivity between methodological procedures to evaluate the AH properties of plant extracts on the same nematode stage.

Clinical evidence to demonstrate that simultaneous growth of epithelial and fibroblast cells is essential for deep wound healing

ObjectiveThe aim of this study was to evaluate the chronic wound healing properties of tannin rich plant extracts. MethodsThe cell growth stimulating potential of 128 procyanidin rich plant extracts was evaluated in in vitro cell culture models. For clinical trial, a 3% solution of two plant extracts having synergistic effect on cell growth was prepared in glycerol and honey. Placebo test product contained only glycerol and honey. 93 adult patients with one or more lower extremity deep wounds were divided at randomly in two groups. 41 patients in the placebo (AS-22) and 52 in the active treatment (AS-21) groups having respectively 49 and 69 wounds of a mean surface area of 56.70 and 52.03cm2, and volume of 57.22 and 52.15cm3, were treated by applying the test products topically for a period of 6-weeks. ResultsA statistically significant difference was observed between the placebo and the AS-21 treated groups with respect to reduction in the wound surface area (33.37 vs 97.87%) and wound volume (29.45 vs 94.17%) after 6-weeks of treatment. Mean wound humidity and pain scores were also reduced. ConclusionTannin rich plant extracts are highly interesting for the treatment of chronic wounds.

Granatapfel: Prävention und adjuvante Ernährungstherapie bei Krebserkrankungen

The pomegranate is one of the oldest fruits cultivated for nutritional and health purposes. However, seven years ago science put a focus on its health effects. Far over 200 peer-reviewed studies have been published so far. Pomegranate juice was shown to have in vitro, in vivo and in clinical studies strong anti-oxidative, anti-inflammatory, anti-arteriosclerotic and anti-carcinogenic properties. In 48 patients with prostate cancer the PSA doubling time was quadrupled. In other studies pomegranate juice was shown to limit the growth of lung, colon, skin and breast cancer. Pomegranate juice improved significantly the myocardial blood-circulation in patients with coronary heart disease and reduced arteriosclerotic lesions of the carotis. It reduces inflammation (through NF-kappa-B and TNF-alpha) and the tendency to develop Alzheimer's disease. Rather than being the result of one particular component, these effects are due to the synergistic activity of all natural biochemical ingredients of the fruit, which modulate cellular signal transduction pathways as well as epigenetic expression and regulation. Pomegranate juice and fermented holistic extracts of the fruit have shown a significantly far greater anti-cancerogenic effect than extracts of isolated pomegranate components such as punicalagin, ellagic acid or tannin rich extracts.

The kinetics of exsheathment of infective nematode larvae is disturbed in the presence of a tannin-rich plant extract (sainfoin) both in vitro and in vivo

The mode of action of bioactive plants on gastrointestinal nematodes remains obscure. Previous in vitro studies showed that exsheathment was significantly disturbed after contact with tannin-rich extracts. However, the role of important factors (extract concentration, parasite species) has not been assessed and no information is available on the occurrence in vivo. These questions represent the objectives of this study. The model incorporated the parasites Haemonchus contortus and Trichostrongylus colubriformis with sainfoin as the bioactive plant. A set of in vitro assays was performed, measuring the changes observed, after 3 h of contact with increasing concentrations of sainfoin, on the rate of artificial exsheathment. The results indicated that sainfoin extracts interfered with exsheathment in a dose-dependent manner and the process overall was similar for both nematodes. The restoration of control values observed after adding PEG to extracts confirms a major role for tannins. A second study was performed in vivo on rumen-cannulated sheep fed with different proportions of sainfoin in the diet to verify these in vitro results. The consumption of a higher proportion of sainfoin was indeed associated with significant delays in Haemonchus exsheathment. Overall, the results confirmed that interference with the early step of nematode infection might be one of the modes of action that contributes to the anthelmintic properties of tanniniferous plants.

Different Polyphenolic Components of Soft Fruits Inhibit α-Amylase and α-Glucosidase

Polyphenol-rich extracts from soft fruits were tested for their ability to inhibit alpha-amylase and alpha-glucosidase. All extracts tested caused some inhibition of alpha-amylase, but there was a 10-fold difference between the least and most effective extracts. Strawberry and raspberry extracts were more effective alpha-amylase inhibitors than blueberry, blackcurrant, or red cabbage. Conversely, alpha-glucosidase was more readily inhibited by blueberry and blackcurrant extracts. The extent of inhibition of alpha-glucosidase was related to their anthocyanin content. For example, blueberry and blackcurrant extracts, which have the highest anthocyanin content, were the most effective inhibitors of alpha-glucosidase. The extracts most effective in inhibiting alpha-amylase (strawberry and raspberry) contain appreciable amounts of soluble tannins. Other tannin-rich extracts (red grape, red wine, and green tea) were also effective inhibitors of alpha-amylase. Indeed, removing tannins from strawberry extracts with gelatin also removed inhibition. Fractionation of raspberry extracts on Sephadex LH-20 produced an unbound fraction enriched in anthocyanins and a bound fraction enriched in tannin-like polyphenols. The unbound anthocyanin-enriched fraction was more effective against alpha-glucosidase than the original extract, whereas the alpha-amylase inhibitors were concentrated in the bound fraction. The LH-20 bound sample was separated by preparative HPLC, and fractions were assayed for inhibition of alpha-amylase. The inhibitory components were identified as ellagitannins using LC-MS-MS. This study suggests that different polyphenolic components of fruits may influence different steps in starch digestion in a synergistic manner.

Efficacy of plant extracts rich in secondary constituents to modify rumen fermentation

Three plant extracts with different secondary constituents were simultaneously evaluated in an eight fermenter rumen simulation technique (Rusitec) for their effects on ruminal fermentation pattern. Specifically, a Yucca schidigera extract containing the saponin compound sarsaponin was supplied at three concentrations (1, 20 and 100 mg sarsaponin/kg dry matter (DM)) and was compared to a Castanea sativa wood extract containing hydrolysable tannins (0.5 and 2.5 g tannins/kg) and pure sulphonate-free lignin (2.5 g/kg). The supplements were added to a basal diet (grass silage, barley grain, grass hay) with a low crude protein (CP) content. These diets were compared to the same, unsuppplemented basal diet (control) and to a diet with additional soybean meal providing protein according to recommendations for dairy cow diets. The control diet and the soybean meal diet differed in rumen fluid ammonia concentration by 15% (13.6 mmol/l versus 16.0 mmol/l). Relative to the control diet, the high doses of the saponin-rich and the tannin-rich extract reduced the rumen fluid ammonia level by up to 21%. There was a tendency for elevated levels of apparent protein degradation during 48 h of fermentation, suggesting that the effect of the extracts on ammonia probably did not result from suppression of microbial protein degradation. Bacterial and protozoal counts in rumen fluid were not influenced by dietary treatments. Substantive effects of the saponin-rich and tannin-rich products on ruminal nitrogen metabolism were observed only at doses exceeding those recommended by the manufacturers.

Taste thresholds and suprathreshold responses to tannin-rich plant extracts and quinine in a primate species (Microcebus murinus).

Theories of plant chemical defenses discriminate between quantitative digestibility reducers (e.g., tannins) and qualitative toxins (e.g., alkaloids). Since the differential effect on taste of these compounds is poorly known, we recorded ingestive responses of a primate species, Microcebus murinus, to four tannin-rich plant extracts and to quinine, by using the behavioral method of the "two-bottle test." The efficiency of tannic extracts at precipitating protein was measured with the blue BSA method. Inhibition taste thresholds for tannins added to a moderately sweet solution varied between 0.25 and 2 g/l. The threshold for quinine hydrochloride was 0.32 g/l. The profiles of the response/concentration curves established for these astringent and bitter substances were similar, with maximal inhibition of consumption occurring for near-threshold concentrations. The large amounts of quinine required to deter this small-bodied species from feeding were unexpected, given its unspecialized frugivorous/insectivorous diet. We propose that the taste responses of Microcebus to tannins have been shaped in relation to the widespread occurrence of efficient polyphenols in food plants, while low responsiveness to quinine reflects a low risk of ingesting toxic alkaloids when feeding on ripe fruits and insects.

Increased Efficacy of Bacillus thuringiensis subsp. kurstaki m Combination with Tannic Acid

We identified tannic acid as an inexpensive additive that increased the efficacy of sublethal concentrations of Bacillus thuringiensis subsp. kurstaki (Berliner). Tannic acid mimicked the active constituents contained in an aqueous, tannin-rich extract of Taxus baccata (L.) bark that retarded development of Heliothis virescens (F.) larvae at 10,000 ppm; most larvae remained in first and second stage when treated with 250-10,000 ppm of tannic acid. Instar development of Trichoplusia ni (Hübner) larvae was affected in a concentration-dependent manner by 2.5-500 ppm of tannic acid. In subsequent bioassays, tannic acid at 25-500 ppm in combination with B. thuringiensis (1.63 micrograms [AI]/ml diet) yielded mean mortalities of 57-75%, whereas treatments with B. thuringiensis alone produced 10% mortality. Mean mortalities in the 3.0, 4.5, and 6.75 micrograms (AI) B. thuringiensis per milliliter of diet treatments (5.5; 8.0, and 30%, respectively) were significantly higher in the presence of 250 and 2,500 ppm tannic acid; in these treatments we observed 78-94% mortality. Addition of tannic acid increased the activity of concentrations of 3-4.5 micrograms (AI) B. thuringiensis per milliliter of diet to approximately that of a concentration of 13 micrograms (AI) B. thuringiensis per milliliter of diet alone (85-95% mortality). Although deaths caused by a formulation of B. thuringiensis + tannic acid occurred more slowly than with high rates of B. thuringiensis alone, such formulations would have the advantages of arresting development, minimizing foliar damage, and decreasing the concentration of B. thuringiensis used.