Yield Of Crude Extract Research Articles

Parametric Evaluation of Microwave–Assisted Extraction of Phenolics from C. domestica Val.

Conventional methods for the extraction of natural products from plant are characterised by the consumption of large volumes of solvent, energy, lengthy extraction procedures and the potentially deleterious degradation of labile compounds. In the last two decades there has been an increasing demand for new extraction techniques, amenable to automation, with shortened extraction times, reduced organic solvent consumption, prevention pollution in analytical laboratories and reducing sample preparation costs. Unmodified domestic microwave oven is used in the extraction of phenolicsfrom C. domestica Val. using water as solvent. The Microwave Assisted Extraction produced a better yield of crude extract of 48 mg compared to Soxhlet extraction methods with only an extraction yield 3.4 mg. Effects of extraction time, microwave power and solvent volume are evaluated on the extraction of phenolic compounds.

Supercritical Carbon Dioxide Extraction of Seed Oil from Winter Melon (Benincasa hispida) and Its Antioxidant Activity and Fatty Acid Composition

In the present study, supercritical carbon dioxide (SC-CO2) extraction of seed oil from winter melon (Benincasa hispida) was investigated. The effects of process variables namely pressure (150–300 bar), temperature (40–50 °C) and dynamic extraction time (60–120 min) on crude extraction yield (CEY) were studied through response surface methodology (RSM). The SC-CO2 extraction process was modified using ethanol (99.9%) as co-solvent. Perturbation plot revealed the significant effect of all process variables on the CEY. A central composite design (CCD) was used to optimize the process conditions to achieve maximum CEY. The optimum conditions were 244 bar pressure, 46 °C temperature and 97 min dynamic extraction time. Under these optimal conditions, the CEY was predicted to be 176.30 mg-extract/g-dried sample. The validation experiment results agreed with the predicted value. The antioxidant activity and fatty acid composition of crude oil obtained under optimized conditions were determined and compared with published results using Soxhlet extraction (SE) and ultrasound assisted extraction (UAE). It was found that the antioxidant activity of the extract obtained by SC-CO2 extraction was strongly higher than those obtained by SE and UAE. Identification of fatty acid composition using gas chromatography (GC) showed that all the extracts were rich in unsaturated fatty acids with the most being linoleic acid. In contrast, the amount of saturated fatty acids extracted by SE was higher than that extracted under optimized SC-CO2 extraction conditions.

Optimization of the culture condition for an antitumor bacterium Serratia proteamacula 657 and identification of the active compounds

Exploration of novel active anti-tumor compounds from marine microbes for pharmaceutical applications has been a continuously hot spot in natural product research. Bacterial growth and metabolites may greatly vary under different culture conditions. In this study, the effects of different culture conditions and medium components on the growth and bioactive metabolites of Serratia proteamacula 657, an anti-tumor bacterium found in our previous study, were investigated. The results showed that lower temperature, weak acidic condition and solid fermentation favored the bacterial growth and the production of active compounds. Four components in the culture medium, NaCl, peptone, yeast extract and MgSO4, were found important to the bacterial growth and active compounds production in medium optimization. Under the optimized condition of solid state fermentation at pH 6.0-7.0, 23-25 °C, with the MgSO4-free medium containing 10.0 g/L peptone, 1.0 g/L yeast extract and 19.45 g/L NaCl, the antitumor activity of S. proteamacula 657 and the yield of crude extracts increased about 15 times and 6 times than the sample obtained in the original liquid fermentation, respectively. The active components in the metabolites of S. proteamacula 657 were identified as a homolog of prodigiosin, a red bacterial pigment, based on the analysis of the NMR and GC-MS. The bacterium S. proteamacula 657, which is adapted to lower temperature, produced prodigiosin-like pigments with highly antitumor activity, suggesting the bacterium is a potential new source for prodigiosin production.

Optimization of Ultrasound-Assisted Extraction of Crude Oil from Winter Melon (Benincasa hispida) Seed Using Response Surface Methodology and Evaluation of Its Antioxidant Activity, Total Phenolic Content and Fatty Acid Composition

In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was investigated through response surface methodology (RSM). Process variables were power level (25–75%), temperature (45–55 °C) and sonication time (20–40 min). It was found that all process variables have significant (p < 0.05) effects on the response variable. A central composite design (CCD) was used to determine the optimum process conditions. Optimal conditions were identified as 65% power level, 52 °C temperature and 36 min sonication time for maximum crude yield (108.62 mg-extract/g-dried matter). The antioxidant activity, total phenolic content and fatty acid composition of extract obtained under optimized conditions were determined and compared with those of oil obtained by the Soxhlet method. It was found that crude extract yield (CEY) of ultrasound-assisted extraction was lower than that of the Soxhlet method, whereas antioxidant activity and total phenolic content of the extract obtained by ultrasound-assisted extraction were clearly higher than those of the Soxhlet extract. Furthermore, both extracts were rich in unsaturated fatty acids. The major fatty acids of the both extracts were linoleic acid and oleic acid.

Evaluation of the effect of crude extract purity and pure paclitaxel content on the increased surface area fractional precipitation process for the purification of paclitaxel

This study evaluated the effect of crude extract purity and pure paclitaxel content on the behavior in terms of purity, yield, fractional precipitation time, and precipitate shape and size of fractional precipitation in the increased surface area fractional precipitation process for the purification of paclitaxel. With increased pure paclitaxel content and crude extract purity, the purity and yield of paclitaxel were improved and the fractional precipitation time was reduced. Regardless of changes in crude extract purity and pure paclitaxel content, it was possible to obtain a small paclitaxel precipitate size by hindering the growth of precipitate particles using an ion exchange resin to increase the surface area. In addition, according to the type of surface-area increasing substance used, precipitate size and shape differed because of a differing affinity for the paclitaxel particles. The lower the crude extract purity and pure paclitaxel content, the higher the yield and the improvement in purity in the process of increased surface area fractional precipitation, with a greater effect on the decrease in paclitaxel particle size.

Effects of high hydrostatic pressure treatments on haemagglutination activity and structural conformations of phytohemagglutinin from red kidney bean (Phaseolus vulgaris)

Red kidney beans were subjected to high hydrostatic pressure (HHP) treatment (50, 150, 250, 350, 450MPa) and phytohaemagglutinin (PHA) was then extracted by affinity chromatography. It appeared that HHP treatment could increase crude extract yield and decrease its haemagglutination activity. For purified samples, PHA yield was not affected at pressures <450MPa while the haemagglutination activity was noticeably reduced at 450MPa. The structural changes were investigated using electrophoresis, size exclusion chromatography (SEC), Fourier transform infrared (FTIR) and differencial scanning calorimetry (DSC). Electrophoresis and SEC profiles revealed a new high molecular weight polymer after 450MPa treatment. At pressures <450MPa, FTIR showed an increase in β-sheet structure and a decrease in α-helix. At 450MPa, the bands at 1688cm−1, representing aggregate strands and random coils, increased. The conclusions are that pressures <450MPa can cause PHA unfolding and induce PHA aggregation at 450MPa.

Antioxidant Property Enhancement of Sweet Potato Flour under Simulated Gastrointestinal pH

Sweet potato is known to be rich in healthful antioxidants, but the stability of its antioxidant properties under gastrointestinal pH is very much unknown. Hence, this study aimed to evaluate the changes in antioxidant properties (total contents of phenolics and flavonoids as well as antioxidant activity) of sweet potato flour (SPF) under simulated gastrointestinal pH conditions. It was found that the yield of SPF crude phenolic extract increased from 0.29 to 3.22 g/100 g SPF upon subjection to gastrointestinal pH conditions (p < 0.05). Also elevated significantly were the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of SPF (p < 0.05). In summary, the antioxidant properties of SPF were enhanced under gastrointestinal pH conditions, suggesting that SPF might possess a considerable amount of bound phenolic and other antioxidative compounds. The antioxidant properties of SPF are largely influenced by pH and thus might be enhanced during the in vivo digestive process.

&lt;b&gt; PHYSICO-CHEMICAL QUALITY CONTROL AND DOSAGE OF TOTAL POLYPHENOLS, FLAVONOIDS OF Morus alba LEAVES (MORACEAE) &lt;/b&gt;

To establish parameters for quality control ofMorus alba leaves were done tests of purity by determining the loss on drying, foreign matter, total ash, acid insoluble ash, swelling index, bitterness index, yield of crude extract, pH and organoleptic properties. The tests were done with samples collected on March, June, September and December, which were according to Brazilian Pharmacopeia and World Health Organization.Through 70 % ethanol extracts of M. alba leaves it was done the dosage of total polyphenols and flavonoids, which were used, respectively, the acidgallic and rutin standards.

Variation in yield and composition of crude bark extracts of P. africana in different provenances of Kenya

Prunus africana's bark extract is used in treatment of prostate gland disorders among other uses. The dwindling of the species abundance in the wild necessitates its domestication. The first step is identification of desired germplasm. In this study, bark extracts from different Kenyan forest zones were compared for yield and chemical composition. Extraction was done using Debat (1974) procedure, while chemical composition was determined using chromatographic procedures. The extract yield showed a positive correlation with tree age, the best source being medium sized trees (30–50 cm dbh). Timboroa provenance had the highest extract yield (1.9%) while Kobujoi had the least (0.73%). Gas Liquid Chromatography analysis showed that Kakamega's extract had the highest number of compounds (8) and Eburu had the highest β-Sitosterol content. With Thin Layer Chromatography, Kinale provenance showed the highest number of compounds (11). The species diversity is therefore important for breeding purposes and should be conserved.

Laboratory and field evaluation of medicinal plant extracts against filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae).

The present study explored the effects of Jatropha curcas, Hyptis suaveolens, Abutilon indicum, and Leucas aspera tested against third instar larvae of filarial vector, Culex quinquefasciatus. The dried plant materials were powdered by an electrical blender. From each sample, 500 g powder was macerated with 1.5 L of hexane, chloroform, ethyl acetate, and methanol 8h, using Soxhlet apparatus, and filtered. The extracts were concentrated at reduced temperature on a rotary evaporator and stored at a temperature of 4°C. The yield of crude extract was 11.4, 12.2, 10.6, and 13.5 g in hexane, chloroform, ethyl acetate, and methanol, respectively. The hexane, chloroform, ethyl acetate, and methanol extract of J. curcas with LC(50) values of 230.32, 212.85, 192.07, and 113.23 ppm; H. suaveolens with LC(50) values of 213.09, 217.64, 167.59, and 86.93 ppm; A. indicum with LC(50) values of 204.18, 155.53, 166.32, and 111.58 ppm; and L. aspera with LC(50) values of 152.18, 118.29, 111.43, and 107.73 ppm, respectively, against third instar larvae of C. quinquefasciatus. The larval mortality was observed after 24 h of exposure. Maximum larvicidal activity was observed in the methanolic extract followed by ethyl acetate, chloroform, and hexane extract. No mortality was observed in the control. The observed mortality were statistically significant at P < 0.05 level. L. aspera showed the highest mortality rate against the mosquito larvae in laboratory and field. The larval density was decreased after the treatment of plant extracts at the breeding sites (sewage water), and hence, these plant extracts of the suitable alternatives of synthetic insecticides for the mosquito vector management. The present results suggest that the medicinal plants extract was an excellent potential for controlling filarial vector, C. quinquefasciatus.

감마선 조사가 미역귀 조다당의 추출수율 및 미백활성 변화에 미치는 영향

본 연구에서는 해조류에 대한 방사선의 영향 평가에 관하여 알아보기 위하여 감마선 조사된 미역귀로부터 추출된 조다당의 추출수율 및 미백활성에 관하여 관찰하였다. 미백활성은 melanin 합성에 중요하게 작용하는 tyrosinase 억제 활성과 melanocyte의 melanin 생성 억제능을 평가하였다. 실험 결과, 방사선의 조사는 선량 의존적으로 조다당의 추출수율을 증가시키고, tyrosinase 억제 활성 및 α-MSH로 melanin을 과생성 시킨 B16BL6 melanoma 세포내 melanin 생성 억제 활성을 유지시켜 주는 것으로 나타났다. 이러한 결과로 미루어 보아 감마선의 조사는 미백활성을 갖는 미역귀 조다당을 얻기 위한 효과적인 방법이며, 미백 산업 분야에서도 효과적으로 이용될 수 있을 것으로 사료된다.

Protein-binding and antioxidant potential of phenolics of mangosteen fruit (Garcinia mangostana)

Phenolics were extracted from mangosteen fruit parts with 70% (v/v) aqueous acetone. The yield of crude extracts of phenolics (CP) ranged from 5.8% to 7.9%. The total phenolics (TPH) content ranged from 9.3mg to over 250mg of gallic acid equivalents per g of extract in the edible aril and skin, respectively. The formation of phenolic–protein complexes was assayed by both the dye-labelled bovine serum albumin (BSA) and the fluorescence quenching methods. Phenolics from peel and rind displayed a strong protein-precipitating potential. On the other hand, phenolics from edible aril exhibited greater affinity for BSA, as determined by the fluorescence quenching assay. The static quenching was the dominant mode of quenching of BSA fluorescence by mangosteen fruit phenolics. Mangosteen phenolics occupied two binding sites on BSA molecules located most likely in or near both tryptophan residues in the BSA molecule acting as an intrinsic fluorescence probe.

Optimization of Supercritical Carbon Dioxide Extraction of Bioactive Flavonoid Compounds from Spearmint (Mentha spicata L.) Leaves by Using Response Surface Methodology

The bioactive flavonoid compounds of spearmint (Mentha spicata L.) leaves were obtained by using supercritical carbon dioxide (SC-CO2) extraction. Extraction was carried out according to face-centred central composite design, and independent variables were pressure (100, 200 and 300 bar), temperature (40, 50 and 60 °C) and co-solvent amount (3, 6 and 9 g/min). The extraction process was optimized by using response surface methodology for the highest crude extraction yield of bioactive flavonoid compounds. The optimal conditions were identified as 209.39 bar pressure, 50.00 °C temperature and 7.39 g/min co-solvent amount. The obtained extract under optimum SC-CO2 condition was analysed by high-performance liquid chromatography. Seven bioactive flavonoids including catechin, epicatechin, rutin, luteolin, myricetin, apigenin and naringenin were identified as major compounds. The results of quantification showed that spearmint leaves are potential source of antioxidant compounds.

Comparison of different extraction methods for the extraction of major bioactive flavonoid compounds from spearmint ( Mentha spicata L.) leaves

Different bioactive flavonoid compounds including catechin, epicatechin, rutin, myricetin, luteolin, apigenin and naringenin were obtained from spearmint ( Mentha spicata L.) leaves by using conventional soxhlet extraction (CSE) and supercritical carbon dioxide (SC-CO 2) extraction at different extraction schemes and parameters. The effect of different parameters such as temperature (40, 50 and 60 °C), pressure (100, 200 and 300 bar) and dynamic extraction time (30, 60 and 90 min) on the supercritical carbon dioxide (SC-CO 2) extraction of spearmint flavonoids was investigated using full factorial arrangement in a completely randomized design (CRD). The extracts of spearmint leaves obtained by CSE and optimal SC-CO 2 extraction conditions were further analyzed by high performance liquid chromatography (HPLC) to identify and quantify major bioactive flavonoid compounds profile. Comparable results were obtained by optimum SC-CO 2 extraction condition (60 °C, 200 bar, 60 min) and 70% ethanol soxhlet extraction. As revealed by the results, soxhlet extraction had a higher crude extract yield (257.67 mg/g) comparing to the SC-CO 2 extraction (60.57 mg/g). Supercritical carbon dioxide extract (optimum condition) was found to have more main flavonoid compounds (seven bioactive flavonoids) with high concentration comparing to the 70% ethanol soxhlet extraction (five bioactive flavonoids). Therefore, SC-CO 2 extraction is considered as an alternative process compared to the CSE for obtaining the bioactive flavonoid compounds with high concentration from spearmint leaves.

Antitumor-Promoting Effects of Polyphenolic Extracts from Seedless and Seeded Indian Grapes

Grapes, the widely consumed fruits, are rich in polyphenols. The biological and chemopreventive activities of grape seed polyphenols have been demonstrated, while similar information regarding crude polyphenolic extracts from whole grapes and their components (pulp plus skin, seeds), particularly the seedless varieties, is lacking. Cancer chemoprevention can be achieved by inhibition of either initiation or promotion/progression stages of carcinogenesis. This study involves the determination of the polyphenolic content extracted from green (Pandhari sahebi, Thompson seedless) and black cultivars (Bangalore blue, Sharad seedless) of Indian grapes and their components (whole grapes, pulp plus skin, and seeds). Comparative evaluation of antitumor-promoting effects of seedless and seeded grape polyphenolic extracts (GPEs) was carried out in carcinogen-initiated and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted S/RVCri-ba mouse skin and stomach, as well as esophagus of ICRC mice. The yield of crude polyphenolic extracts from whole grapes and their components varied between 3% and 51%. The total polyphenolic content expressed as mg catechin equivalents/g crude polyphenolic extract ranged from 0.47 to 701 in seeded grapes and 1.49 to 28.30 in seedless varieties. Both seedless and seeded GPEs possessed antitumor-promoting activity in target tissues of mice as is evident from their ability to delay tumor formation along with a significant decrease in tumor multiplicity and incidence. Marked and sustained epidermal hyperplasia observed in 7,12-dimethylbenz(a)anthracene-initiated and TPA-promoted mice was greatly reduced on pretreatment with GPE or catechin. The polyphenolic extracts from Sharad seedless and seeds of Bangalore blue showed the strongest suppressing activity comparable to catechin than the corresponding whole grapes. The results suggest that the chemopreventive activity of polyphenols extracted from seedless grape cultivars was as effective as that of the seeded variety and these may have beneficial effects in disease states, especially cancer.

Characterization of hydrogenase from purple sulfur bacterium Thiocapsa roseopersicina and its prolonged in vitro hydrogen evolution

Hydrogenase from a purple sulfur bacterium, Thiocapsa roseopersicina NCIB 8347, was purified, characterized and investigated for in vitro hydrogen ( H 2 ) production. The cell concentration and the specific hydrogenase activity were increased when T. roseopersicina NCIB 8347 was photo-autotropically cultivated with the addition of nutrients every 24 h. Crude extracts of the cells were prepared by sonication and then subjected sequentially to ultra-centrifugation, ammonium sulfate fractionation and heat-treatment to remove the impurities. Four-step separation of chromatographic procedures utilizing Q-Sepharose, Phenyl Superose, Mono-Q and Superdex resulted in a 9.56-fold purification with a 0.25% yield of crude cell extract. The optimum pH and temperature for the H 2 evolution of the purified enzyme was 7.0 and 70 °C, respectively, and those for optimum cell growth were 7.0 and 25 °C, respectively. The maximum H 2 -evolution activity was exhibited at 70 °C, and when the reaction temperature was decreased to 50 °C, the manifest activity fell to 44%. Hydrogenase activities were initially increased in the course of the 50–70 °C heat-treatment, whereas the remaining activities after 5-h heat-treatment at 50 and 70 °C were 110% and 60% of the initial ones, respectively. The purified hydrogenase, at 50 °C and pH 7.0, evolved H 2 gas for approximately 10 days under in vitro conditions, using sodium dithionite and methyl viologen as the electron donor and carrier, respectively.

Extraction of bio-active components from Rhodiola sachalinensis under ultrahigh hydrostatic pressure

A new extraction technique, ultrahigh hydrostatic pressure (UHP), was used to obtain bio-active components from Rhodiola sachalinensis. The leaching-out rates of flavones and salidroside were measured under different conditions. The extraction efficiency of different extraction methods and the DPPH radical scavenging activities of their crude extracts were investigated. The optimal conditions of extracting flavones and salidroside were as follows: 41 or 60% (v/v) of ethanol concentration, 70:1 ml/g of solvent–herb ratio, and 500 MPa of hydrostatic pressure for 3 min. The leaching-out rate of flavones and salidroside was up to 5.233 and 0.411%, respectively. The yield of crude extract of UHP was up to 26.116%, comparing with the crude extract was 13.825% by reflux and 16.995% by soxhlet. The UHP extraction technique showed high efficiency in extracting bio-active components at room temperature. The crude extract had stronger DPPH radical scavenging activity than TBHQ.

Comparison of Free Radical Scavenging Activity of Siamese Neem Tree (Azadirachta indica A. Juss var. siamensis Valeton) Leaf Extracts Prepared by Different Methods of Extraction

Objective: The aim of this study was to investigate the antioxidant activity of the aqueous extracts of leaves of Siamese neem tree (Azadirachta indica A. Juss var. siamensis Valeton) from several extracting and drying methods using 2,2-diphenyl-1-picrylhydrazyl (DPPH)-scavenging assay. Materials and Methods: The leaves of Siamese neem tree were extracted using percolation, decoction, maceration, soxhlet extraction, freeze drying or spray drying methods. The extract was tested for antioxidant activity using DPPH-scavenging assay. Thin-layer chromatography of the extract from decoction was also investigated. Results: The freeze drying method gave the highest yield (51.50%, w/w) of crude extract, while decoction gave the most effective DPPH-scavenging activity (EC₅₀: 31.4 µg/ml). Thin-layer chromatography analysis was used to screen the leaf extract obtained using decoction, and the chromatogram showed spots corresponding to quercetin and rutin flavonoids which exhibited antioxidant activities (EC₅₀: 2.29 and 34.67 µg/ml, respectively). Conclusion: Siamese neem tree leaf extracts possessed free radical scavenging activity against the DPPH radical. The most active extract was obtained with the leaf decoction method. It showed antioxidant activity with EC₅₀ of 31.4 µg/ml.

Fractional precipitation for paclitaxel pre-purification from plant cell cultures of Taxus chinensis

Fractional precipitation is a simple and efficient procedure for pre-purification of paclitaxel. The optimal methanol composition in water, paclitaxel content in crude extract, storage temperature, and time were 61.5% (v/v), 0.5% (w/v), 0 °C, and 3 days, respectively. As purity of the paclitaxel in the crude extract increases, the purity and yield of paclitaxel from fractional precipitation increases. This pre-purification process serves to minimize the solvent usage, size and complexity of the HPLC operations for paclitaxel purification. This process is readily scalable to a pilot plant and eventually to a production environment where multikilogram quantities of material are expected to be produced.

Intracolonial variation in chemical defenses of the sponge Cacospongia sp. and its consequences on generalist fish predators and the specialist nudibranch predator Glossodoris pallida

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 168:187-196 (1998) - doi:10.3354/meps168187 Intracolonial variation in chemical defenses of the sponge Cacospongia sp. and its consequences on generalist fish predators and the specialist nudibranch predator Glossodoris pallida Mikel A. Becerro*, Valerie J. Paul, John Starmer University of Guam Marine Laboratory, Mangilao, Guam 96923, USA *Present address: Center for Advanced Studies at Blanes (CSIC), Cami de Sta Barbara s/n, E-17300 Blanes (Girona), Spain. E-mail: mikel@ceab.csic.es ABSTRACT: On Guam, the nudibranch Glossodoris pallida specializes in feeding on the branching sponge Cacospongia sp., which contains scalaradial and desacetylscalaradial as major secondary metabolites. The nudibranch, which accumulates both compounds for its own defense, is typically found on the base of the sponge. In this study, we quantified intracolonial variation in the production of secondary metabolites (percent yield of crude extract, filtered extract, scalaradial, and desacetylscalaradial), structural material (fiber and ash content), and protein content in Cacospongia sp. in order to assess the consequences that such variation has on feeding responses of generalist fish predators, the specialist nudibranch predator G. pallida, and on the distribution of the nudibranch on the sponge. Levels of secondary metabolites varied among the parts of the sponge analyzed (tip, base, surface, and matrix). The mean percent yield of crude extract was higher in the surface of the sponge, while filtered extract and desacetylscalaradial were higher in tips than in bases. Structural materials were highest in the base and in the surface of the sponge. In contrast, the inner part of the sponge contained higher levels of protein than the surface, but no differences were found between tips and bases. Compared to a control, the crude extract of Cacospongia sp. significantly deterred fish feeding at the lowest concentration found in the sponge (base concentration) in field assays. When offered a choice between base and tip concentrations, both the pufferfish Canthigaster solandri in laboratory assays and the natural reef fish assemblage in the field showed no preference for extracts of bases over tips (i.e. lower levels over higher levels of chemical defenses). However, when offered a choice between pieces of sponge from the base and from the tip, the nudibranch G. pallida preferred bases over tips, which agrees with the nudibranch distribution on the sponge. Alternative factors may shape the observed distribution of nudibranchs on Cacospongia sp. Nudibranchs at the bases may suffer lower levels of predation because they are less accessible to predators than nudibranchs at the tips of the sponge. Therefore, we also tested whether small disks of artificial squid food located on tips and bases of the sponge are equally accessible to generalist fish predators. The reef fish C. solandri in laboratory assays and the natural fish assemblage at the Cacospongia sp. community consumed equal amounts of food from tips and bases. Our data demonstrate that Cacospongia sp. extracts deter feeding by fishes at the lowest concentration found in the sponge, which suggests that the higher concentration in the tips is not a mechanism to avoid consumption by generalist fish predators. In contrast, avoidance of higher levels of chemistry appears to be the factor behind the selection of bases over tips by the specialist nudibranch predator G. pallida. Intracolonial variation in chemical defenses seems to determine the nudibranch distribution on the sponge. KEY WORDS: Chemical defenses · Within-colony variation · Antipredatory role · Generalist versus specialist predators · Glossodoris pallida · Cacospongia sp. Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 168. Publication date: July 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.