Holistic protocol for callus culture optimization using statistical modelling

Plants endue a key role against illnesses caused by oxidative stress. These attributes are frequently associated with polyphenolic compounds. However, presence and concentration of secondary metabolites are affected by abiotic factors. The in vitro culture techniques can solve these drawbacks. Peppers can be a suitable alternative to obtain polyphenols. Aiming to optimise the callus culture stage from Capsicum baccatum to produce polyphenols, this work evaluated systemically the effects of the explant’s origin (root, hypocotyl and cotyledon), growth hormone type (2,4-dichlorophenoxyacetic acid (2,4-D), benzylaminopurine (BAP) and a combination of 2,4-D/BAP at five-to-one ratio) and concentration (0.023–10.000 mg L^?1) on callus culture efficiency parameters using a multilevel factorial design. The root explant in combination with BAP at 1.138 mg L^?1 ensured the optimal values of the assessed responses; ?callus mass (225.03 mg), antioxidant activity (35.95%), total phenols (11.48 mg of GAE/g DE) and flavonoids (15.92 mg of RU/g DE) production.     

Plant Regeneration Through Callus Organogenesis and True-to-Type Conformity of Plants by RAPD Analysis in Desmodium gangeticum (Linn.) DC.

An efficient plant regeneration protocol was established for an endangered ethnomedicinal plant Desmodium gangeticum (Linn.) DC. Morphogenic calli were produced from 96 % of the cultures comprising the immature leaf explants on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (4.0 mg?l^?1) in combination with 6-benzylaminopurine (BA; 0.8 mg?l^?1). For callus regeneration, various concentrations of BA (1.0–5.0 mg?l^?1) or thidiazuron (TDZ; 1.0–5.0 mg?l^?1) alone or in combination with indole-3-acetic acid (IAA; 0.2–1.0 mg?l^?1) were used. Highest response of shoot regeneration was observed on MS medium fortified with TDZ (4.0 mg?l^?1) and IAA (0.5 mg?l^?1) combination. Here, 100 % cultures responded with an average number of 22.3 shoots per gram calli. Inclusion of indole-3-butyric acid in half MS medium favored rooting of recovered shoots. Out of 45 rooted plants transferred to soil, 40 survived. Total DNA was extracted from the leaves of the acclimatized plants of D. gangeticum. Analysis of random amplified polymorphic DNA using 13 arbitrary decanucleotide primers showed the genetic homogeneity in all the ten plants regenerated from callus with parental plant, suggesting that shoot regeneration from callus could be used for the true-to-type multiplication of this plant.     

Effect of Various Growth Hormone Concentration and Combination on Callus Induction,Nature of Callus and Callogenic Response of Nerium odorum

Nerium odorum, Linn. (Apocynaceae) is an important evergreen shrub. It is heat, salinity and drought tolerant. Plants with milky sap have medicinal value, mainly cardenolides, flavonoids and terpenes. It is used for wastewater purification and for restoration of riparian woodlands. In view of these facts, the study was conducted for micropropagation of N. odorum. Murashige and Skoog (MS) media supplemented with different concentrations (0.5–10.0 mg/l) of 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BAP) and kinetin (Kin) were used singly and in combinations. Among all the growth hormones, 2,4-D was the best for callus induction (75 % in stem and 79 % in leaf) and in combination 2,4-D and BAP (78 % in stem and 81 % in leaf). The day of callus induction started from the 19th to the 37th day. This variation is due to the differences in culture conditions and the age of explants. The fresh and dry weight and moisture content showed good growth of callus, which is used in further studies of alkaloid production. Micropropagation of this plant allows the production of clones at a fast rate and in continuous manner. This work can lead to the development of an efficient protocol for callus induction and other issues.     

Regeneration and Agrobacterium-mediated transformation of the apomictic species Eulaliopsis binata

Protocols for regeneration and Agrobacterium-mediated transformation of the apomictic species Eulaliopsis binata were developed. Initially, seeds of four genotypes of E. binata were incubated on a callus induction Murashige and Skoog (MS) basal medium supplemented with three concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D). It was found that 36.2 % of explants developed highly friable callus on medium containing 3.0 mg l^?1 2,4-D. Based on frequency of callus induction, the genotype Neixiang was selected for regeneration and transformation. Callus incubated on MS basal medium supplemented with 0.2 mg l^?1 α-naphthalene acetic acid and 6.0 mg l^?1 6-furfuryl-aminopurine developed shoots. Subsequently, Agrobacterium tumefaciens strain EHA105—harboring a plasmid pCAMBIA1381 carrying a hygromycin phosphotransferase (hpt) resistance gene and a synthetic green fluorescent protein (GFP) gene, both driven by the cauliflower mosaic virus 35S promoter—was used for transformation system. Putative transgenic callus was obtained following two cycles of hygromycin selection. Expression of the transgene(s) in putative transgenic callus was analyzed using the GFP detection. Molecular identification of putative transformed shoots was performed by polymerase chain reaction and Southern blot analysis to confirm presence and integration of the hpt gene.     

Shoot Multiplication and Callus Induction of Labisia pumila var. alata as Influenced by Different Plant Growth Regulators Treatments and Its Polyphenolic Activities Compared with the Wild Plant

This study aims to investigate whether the in vitro-cultured L. pumila var. alata has higher antioxidant activity than its wild plant. An 8-week-old L. pumila var. alata nodal segment and leaf explants were cultured onto Murashige and Skoog (MS) medium supplemented with various cytokinins (zeatin, kinetin, and 6-benzylaminopurine (BAP)) for shoot multiplication and auxins (2,4-dichlorophenoxyacetic acid (2,4-D) and picloram) for callus induction, respectively. The results showed that 2 mg/L zeatin produced the optimal results for shoot and leaf development, and 0.5 mg/L 2,4-D produced the highest callus induction results (60%). After this, 0.5 mg/L 2,4-D was combined with 0.25 mg/L cytokinins and supplemented to the MS medium. The optimal results for callus induction (100%) with yellowish to greenish and compact texture were obtained using 0.5 mg/L 2,4-D combined with 0.25 mg/L zeatin. Leaves obtained from in vitro plantlets and wild plants as well as callus were extracted and analyzed for their antioxidant activities (DPPH and FRAP methods) and polyphenolic properties (total flavonoid and total phenolic content). When compared with leaf extracts of in vitro plantlets and wild plants of L. pumila var. alata, the callus extract displayed significantly higher antioxidant activities and total phenolic and flavonoid content. Hence, callus culture potentially can be adapted for antioxidant and polyphenolic production to satisfy pharmaceutical and nutraceutical needs while conserving wild L. pumila var. alata.     

Production of a new mucilage compound in Lepidium sativum callus by optimizing in vitro growth conditions

The mucilage in Lepidium sativum L. is considered a biologically active compound with diverse medicinal properties. Different explants (hypocotyls and leaf) were transferred to Murashige and Skoog (MS) medium supplemented with twelve different plant growth regulator combinations under two different incubations (light and dark). The best mucilage production from callus (36.76% g g^?1 dry weight) was obtained in the MS medium supplemented with 1 mg L^?1 of 2, 4-D and 2 mg L^?1 of BAP under the light condition. The mucilage produced by callus culture was nearly three times more than the mucilage yield of the seeds. The glucose, arabinose + mannose and galactose were 43.4 (mg g^?1 DW), 195.3 (mg g^?1 DW) and 86.2 (mg g^?1 DW) in the mucilage originated from seed, callus leaf and callus hypocotyl, respectively. The present study proposes an efficient method for producing large scales of mucilage with a favorable sugar aimed at food or pharmaceutical industries.     

Piper nigrum: Micropropagation, Antioxidative enzyme activities, and Chromatographic Fingerprint Analysis for Quality Control

A reliable in vitro regeneration system for the economical and medicinally important Piper nigrum L. has been established. Callus and shoot regeneration was encouraged from leaf portions on Murashige and Skoog (MS) medium augmented with varied concentrations of plant growth regulators. A higher callus production (90 %) was observed in explants incubated on MS medium incorporated with 1.0 mg?L^?1 6-benzyladenine (BA) along with 0.5 mg?L^?1 gibberellic acid after 4 weeks of culture. Moreover, a callogenic response of 85 % was also recorded for 1.0 mg?L^?1 BA in combination with 0.25 mg?L^?1 α-naphthalene acetic acid (NAA) and 0.25 mg?L^?1 2,4-dichlorophenoxyacetic acid or 0.5 mg?L^?1 indole butyric acid (IBA) along with 0.25 mg?L^?1 NAA and indole acetic acid. Subsequent sub-culturing of callus after 4 weeks of culture onto MS medium supplemented with 1.5 mg?L^?1 thiodiazoran or 1.5 mg?L^?1 IBA induced 100 % shoot response. Rooted plantlets were achieved on medium containing varied concentrations of auxins. The antioxidative enzyme activities [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)] revealed that significantly higher SOD was observed in regenerated plantlets than in other tissues. However, POD, CAT, and APX were higher in callus than in other tissues. A high-performance liquid chromatography (HPLC) fingerprint analysis protocol was established for quality control in different in vitro-regenerated tissues of P. nigrum L. During analysis, most of the common peaks represent the active principle “piperine.” The chemical contents, especially piperine, showed variation from callus culture to whole plantlet regeneration. Based on the deviation in chromatographic peaks, the in vitro-regenerated plantlets exhibit a nearly similar piperine profile to acclimated plantlets. The in vitro regeneration system and HPLC fingerprint analysis established here brought a novel approach to the quality control of in vitro plantlets, producing metabolites of interest with substantial applications for the conservation of germplasm.     

Somatic Embryogenesis and Synthetic Seed Production—a Biotechnological Approach for True-to-Type Propagation and In Vitro Conservation of an Ornamental Bulbaceous Plant Drimiopsis kirkii Baker.

An efficient plant regeneration protocol through indirect somatic embryogenesis pathway via callus had been developed from the leaf explant of an ornamental bulbaceous plant Drimiopsis kirkii. Optimum friable calli were induced on Murashige and Skoog (MS) basal medium supplemented with 3.0 mg/l of 2,4-dichlorophenoxyacetic acid and 1.0 mg/l of α-naphthalene acetic acid (NAA). On subculturing the callus on MS medium supplemented with 2.5 mg/l of thidiazuron (TDZ), 73.3 % of the cultures responded with 20.4?±?0.3 somatic embryos (SEs) per 500 mg callus at different stages of development after 6 weeks of culture. The highest response of 86.7 % with 28.3?±?0.5 embryos per 500 mg callus was observed on MS medium supplemented with 2.5 mg/l TDZ and 1.0 mg/l NAA. SEs were encapsulated in calcium alginate beads for the production of synthetic seeds (SSs) and their storability was investigated. The highest SS germination (93.3 %) was observed in 1.0 % sodium alginate followed by 86.7 % germination with 2.5 % sodium alginate. The SSs were stored at three different temperatures (4, 15, and 24?ºC) up to 6 months. The SSs kept at 15 °C showed 64.4 % germinability even after 4 months of storage. Both nonencapsulated and encapsulated SE-derived plants were successfully transferred to soil with 93.3 and 88.3 % survival rate accordingly. Randomly amplified polymorphic DNA (RAPD) analysis revealed that there were no somaclonal variations among the plants produced via somatic embryogenesis and they are true-to-type to their parental plant. These results confirmed the most reliable methods, which can be further used for genetic transformation studies as well as for mass propagation of ornamental D. kirkii at a commercial level.     

Effect of Salts (NaCl and Na2CO3) on Callus and Suspension Culture of Stevia rebaudiana for Steviol glycoside Production

Steviol glycosides are natural non-caloric sweeteners which are extracted from the leaves of Stevia rebaudiana plant. Present study deals the effect of salts (NaCl and Na₂CO₃) on callus and suspension culture of Stevia plant for steviol glycoside (SGs) production. Yellow-green and compact calli obtained from in vitro raised Stevia leaves sub-cultured on MS medium supplemented with 2.0 mg l^?1 NAA and different concentrations of NaCl (0.05–0.20 %) and Na₂CO₃ (0.0125–0.10 %) for 2 weeks, and incubated at 24?±?1 °C and 22.4 μmol m^?2 s^?1 light intensity provided by white fluorescent tubes for 16 h. Callus and suspension biomass cultured on salts showed less growth as well as browning of medium when compared with control. Quantification of SGs content in callus culture (collected on 15th day) and suspension cultures (collected at 10th and 15th days) treated with and without salts were analyzed by HPLC. It was found that abiotic stress induced by the salts increased the concentration of SGs significantly. In callus, the quantity of SGs got increased from 0.27 (control) to 1.43 and 1.57 % with 0.10 % NaCl, and 0.025 % Na₂CO₃, respectively. However, in case of suspension culture, the same concentrations of NaCl and Na₂CO₃ enhanced the SGs content from 1.36 (control) to 2.61 and 5.14 %, respectively, on the 10th day.     

Regeneration-Based Quantification of Coumarins (Scopoletin and Scoparone) in <Emphasis Type="Italic">Abutilon indicum</Emphasis> In Vitro Cultures

Abutilon indicum exploited for its immense value has been propagated successfully through multiple shoot induction and somatic embryogenesis. Direct regeneration (8.20?±?0.83 shoots) was achieved from nodal explants using 0.5 mg/l kinetin (Kn) in MS media. The basal callus from nodal explants turned embryogenic on subsequent introduction of 0.2 mg/l TDZ into the Kn-supplemented media, giving rise to somatic embryos. The embryogenic potential of calli expressed in terms of embryo-forming capacity (EFC) increased from 8.15 EFC to 20.95 EFC after plasmolysis. The phytochemical analysis (HPLC) for the presence of scopoletin and scoparone has revealed a unique accumulation pattern, with higher levels of scopoletin during the earlier stages and scoparone in the later stages of development. The embryogenic calli contained the highest amount of coumarins (99.20?±?0.97 and 61.03?±?0.47 μg/gFW, respectively) followed by regenerated plant (9.43?±?0.20 and 36.36?±?1.19 μg/gFW, respectively), obtained via somatic embryogenesis. Rapid multiplication of A. indicum equipped with two potent coumarins is important in order to meet the commercial demand for combat against dreadful diseases, thereby providing a new platform for plant-based drugs and their manufacture on a commercial scale.     

Candida Biofilm Disrupting Ability of Di-rhamnolipid (RL-2) Produced from Pseudomonas aeruginosa DSVP20

Biosurfactant produced from Pseudomonas aeruginosa DSVP20 was evaluated for its potential to disrupt Candida albicans biofilm formed on polystyrene (PS) surfaces in this investigation. P. aeruginosa DSVP20 exhibited optimum production of biosurfactant (5.8 g?L^?1) after 96 h of growth with an ability to reduce surface tension of the aqueous solution from 72 to 28 mN?m^?1. Analysis of purified biosurfactant with FT-IR, ¹H and ¹³C NMR and MALDI-TOF MS revealed it to be di-rhamnolipid (RL-2) in nature. Biofilm disrupting ability of RL-2 (0.16 mg?mL^?1) on Candida cells when checked using XTT reduction assay revealed that about 50 % of the cells remain adhered to 96-well plate after 2 h of treatment, while up to 90 % reduction in pre-formed C. albicans biofilm on PS surface was observed with RL-2 (5.0 mg?mL^?1) in a dose-dependent manner. Microscopic analyses (SEM and CLSM) further confirm the influence of RL-2 on disruption of Candida biofilm extracellular matrix on PS surface which can be exploited as a potential alternative to the available conventional therapies.     

Piezoelectric immuno sensor for the detection of candida albicans microbes

The system consists of an AT-cut quartz piezoelectric crystal, oscillator and frequency counter. The surface of the palladium-plated electrodes is oxidized anodically, and anti-Candida antibody is immobilized onto the surface. The crystal sensor is dipped into Candida suspension and the surface mass increase, caused by immuno-adsorption of Candida, is measured by the decrease in the resonant frequency of the crystal. The frequency shift is correlated with C. albicans concentrations in the range 10⁶?5 × 10⁸ cells cm^?3. The crystal sensor showed no response to Saccharomyces cerevisiae.     

Production of camptothecin in the elicited callus cultures of <Emphasis Type="Italic">Nothapodytes nimmoniana</Emphasis> (J. Graham) Mabberly

The biotechnological approach of in vitro cultures elicitation offers an alternative strategy for the production of camptothecin (CPT) in Nothapodytes nimmoniana to mitigate indiscriminate harvest of the endangered natural population for the alkaloid. Yeast extract (YE) and vanadyl sulfate (VS) elicitors were used to enhance the biosynthesis of CPT in hypocotyl-derived callus cultures of N. nimmoniana by cultivation using solid and liquid Murashige and Skoog (MS) medium amended with NAA + BAP (2.0 + 1.0 mg L^?1). Effects of the two elicitors on biomass and CPT production at 6.25, 12.5, 25, 50 and 75 mg L^?1 concentrations using callus cultures from three cell lines were evaluated after 15, 30 and 45 days culture. Yeast extract elicitor treatments showed a linear enhancement effect on biomass and CPT production up to 50 mg L^?1 YE and beyond the concentrations, no significant effect was observed. Enhanced biomass and CPT production were achieved with VS elicitor up to 25 mg L^?1 concentrations but, 50 and 75 mg L^?1 VS had minimal effects on biomass and CPT production in callus sources and incubation duration-dependent manner. The intracellular yield of CPT in liquid media-cultivated cultures at concentrations of the two elicitors was lower when compared to solid media treatments relative control due to the extracellular accumulation but, higher overall production. Accumulation of the biomass showed association with produced CPT in the elicitor treatments and control cultures.     

Large inclusion constants of ��-cyclodextrin with carborane derivatives

Complexation of some o-, m- and p-carborane derivatives with ??-cyclodextrin was investigated using phenolphthalein in pH 10.5 (0.05 mol dm^?3) borate buffer. Some carborane derivatives indicated large inclusion constants K_ass > 1 × 10⁵ dm³ mol^?1.     

Kinetics and mechanism of the reduction of μ-adi-di[N,N′-bis{salicylideneethylenediaminatoiron(III)}] by dithionate ion

The kinetics and mechanism of the reduction of the μ-adi-di[N,N′-bis{salicylideneethylenediaminatoiron(III)}] complex, [Fe₂adi], by dithionate ion, S₂O₆ ^2?, have been investigated in aqueous perchloric acid at 29 °C, I = 0.05 mol dm^?3 (NaClO₄) and [H⁺] = 5.0 × 10^?3 mol dm^?3. Spectrophotometric titrations indicated that one mole of the reductant was oxidized per mole of oxidant. Kinetic profiles indicated first-order rate with respect to [Fe₂adi] but zeroth-order dependence on [S₂O₆ ^2?]. The rate of reaction increased with increase in [H⁺], decreased with increased dielectric constant, but was invariant to changes in ionic strength of the medium. Addition of small amounts of AcO^? and Mg²⁺ ions did not catalyse the reaction. A least-squares fit of rate against [H⁺]² was linear (r ² = 0.984) without intercept. The reaction was analysed on the basis of a proton-coupled outer-sphere electron transfer mechanism.     

In Vitro Propagation,Encapsulation, and Genetic Fidelity Analysis of Terminalia arjuna: a Cardioprotective Medicinal Tree

The present study described an improved and reproducible in vitro regeneration system for Terminalia arjuna using nodal segment explants obtained from a mature plant. Shoot tips excised from in vitro proliferated shoots were encapsulated in 3 % sodium alginate and 100 mM CaCl₂?2H₂O for the development of synthetic seeds which may be applicable in short-term storage and germplasm exchange of elite genotype. Shoot multiplication was significantly influenced by a number of factors, namely types and concentrations of plant growth regulators, medium composition, repeated transfer of mother explants, subculturing of in vitro regenerated shoot clumps, agar concentrations, and temperature. Maximum numbers of shoots (16.50?±?3.67) were observed on modified Murashige and Skoog (MMS) medium containing 0.5 mg l^?1 of benzylaminopurine (BAP) and 0.1 mg l^?1 of naphthalene acetic acid (NAA). To shortening the regeneration pathway, rooting of micropropagated shoots under in vitro condition was excluded and an experiment on ex vitro rooting was conducted and it was observed that the highest percentage of shoots rooted ex vitro when treated with indole-3-butyric acid (IBA, 250 mg l^?1)?+?2-naphthoxy acetic acid (NOA, 250 mg l^?1) for 5 min. The well-developed ex vitro rooted shoots were acclimatized successfully in soilrite under greenhouse conditions with 80 % survival of plants. Randomly amplified polymorphic DNA (RAPD) analysis confirmed that all the regenerated plants were genetically identical to the mother plant, suggesting the absence of detectable genetic variation in the regenerated plantlets. To the best of our knowledge, this is the first report on synthetic seed production as well as ex vitro rooting and genetic fidelity assessment of micropropagated shoots of T. arjuna.     

Effects of Phytohormones and Jasmonic Acid on Glucosinolate Content in Hairy Root Cultures of Sinapis alba and Brassica rapa

Although some study have established hairy root cultures from brassicaceous plants with glucosinolates (GS) as characteristic secondary metabolite, studies are missing which compare hairy roots with the corresponding mother plants. Therefore, two different plant species—Sinapis alba and Brassica rapa subsp. rapa pygmeae teltoviensis—were transformed with the Agrobacterium rhizogenes strain A4. Aliphatic and indolyl GS were present in B. rapa, exhibiting larger quantities in leaves than in roots. Aromatic p-hydroxybenzyl GS were found particularly in the leaves of S. alba. However, the proportion of indolyl GS increased suddenly in transformed hairy roots of S. alba and B. rapa. Cultivation with the phytohormone kinetin (0.5 mg?L^?1) enhanced GS accumulation in B. rapa hairy roots, however not in S. alba, but 2,4-D (0.4 mg?L^?1) induced de-differentiation of roots in both species and reduced GS levels. GS levels especially of 1-methoxyindol-3ylmethyl GS increased in hairy roots in response to JA, but root growth was inhibited. While 2 weeks of cultivation in 100 to 200 μM JA were determined at optimum for maximum GS yield in S. alba hairy root cultures, 4 weeks of cultivation in 50 to 100 μM JA was the optimum for B. rapa.     

Applicability of Derivative Spectrophotometry,Bivariate Calibration Algorithm,and the Vierordt Method for Simultaneous Determination of Ranitidine and Amoxicillin in Their Binary Mixtures

Abstract

Ultraviolet (UV)–derivative spectrophotometry, bivariate calibration algorithm, and Vierodt methods were applied to simultaneous determination of ranitidine (R) and amoxicillin (AMX) in binary mixtures. The first-order derivative allows determination of R in the concentration range 4.0 · 10^?6 mol · dm^?3 to 6.0 · 10^?5 mol · dm^?3. Vierordt method enables Ranitidine assaying in the presence of 2.5-fold excess of AMX and 3-fold excess of R. The bivariate calibration method obeys Beer's law in the concentration ranges 4.0 · 10^?6 mol · dm^?3 to 6.0 · 10^?5 mol · dm^?3 for R and 2.0 · 10^?6 to 2.0 · 10^?5 mol · dm^?3 for AMX.     

Improved Protocol for Somatic Embryogenesis and Calcium Alginate Encapsulation in Anethum graveolens L.: A Medicinal Herb

An improved procedure has been developed for efficient somatic embryogenesis in Anethum graveolens. Green friable embryogenic callus was obtained from hypocotyl segments on medium augmented with 2,4-dichlorophenoxyacetic acid (2,4-D). The highest embryogenic callus induction frequency of 87 % was obtained on Murashige and Skoog (MS) medium containing 1.13 μM 2,4-D. At lower concentration of 2,4-D (0.34 μM) callus turned dark in color and slow growing. Embryogenic cultures (76 %) responded with a mean number of 43 globular and 18 heart stage embryos. Somatic embryo maturation and subsequent conversion into plantlets took place on MS lacking growth regulators. Maximum number of somatic embryos developed on MS medium was 128.3 (per flask) and a plantlet conversion of 82 % was observed. Calcium alginate beads were produced by encapsulating somatic embryos. Highest percent germination (83 %) was observed on 0.8 % agar solidified MS medium with the plantlets acquiring an average length of 2.1 cm. Encapsulated somatic embryos could be stored at 4 °C up to 60 days with a conversion frequency of 49.3 %. Highest protein and proline content has been observed in embryogenic callus with small globular embryos. During morphological differentiation of the somatic embryos, changes in the antioxidant enzymatic system were observed. Superoxide dismutase (SOD) activity increased during initial stages and decreased catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) activities were detected.     

Mono-complex formation kinetics of iron(III) with nonsubstituted octane and nonane 2,4-dicarbonyl ligands in aqueous solution

The kinetics and mechanism of the reaction of complexation of iron(III) with 2,4-octanedione and 2,4-nonanedione have been investigated spectrophotometrically in aqueous solution at 10°C and ionic strength 0.5 mol dm^?3 NaClO₄. The equilibrium constants of the mono-complexes have been determined. The mechanism proposed to account for the kinetic data involves a double reversible pathway where both Fe³⁺ and Fe(OH)²⁺ react with the enol tautomer of the ligand. 2,4-Octanedione reacts with Fe³⁺ and Fe(OH)²⁺ with rate constants of 0.65 dm³ mol^?1 s^?1, and 14.07 dm³ mol^?1 s^?1, respectively. For 2,4-nonanedione complexation the rate constants determined are 0.49 dm³ mol^?1 s^?1, and 11.39 dm³ mol^?1 s^?1, respectively. Some discussions are made on the basis of Eigen-Wilkins theory considering the effect of solvent exchange on the complex formation. © 1993 John Wiley & Sons, Inc.