Hydroalcoholic extract of Tagetes minuta L. inhibits inflammatory bowel disease through the activity of pheophytins on the NF-κB signalling pathway.

ETHNO-PHARMACOLOGICAL RELEVANCE: Species of the genus Tagetes are well known for their anti-inflammatory properties. Tagetes minuta "Huacatay" is an endemic species of South America that has been used in traditional medicine since ancient times as a remedy for stomach and intestinal discomfort. AIM OF THE STUDY: The aim of this study is to investigate the anti-inflammatory activity of the aqueous and hydroalcoholic extracts of the Huacatay, identifying the compounds responsible for this activity. MATERIALS AND METHODS: Anti-inflammatory activity of the compounds, fractions and extracts was evaluated in Hs 746T (stomach), HIEC-6 (intestine) and THP-1 (monocytes peripheral blood) cells by measuring their inhibitory capacity against the NF-κB production. RESULTS: Aqueous and hydroalcoholic extracts of Tagetes minuta displayed anti-inflammatory activity in vitro, the hydroalcoholic extract being the most active (IC50 between 59.72 and 66.42 µg/mL) in all cell lines. Bio-guided hydroalcoholic extract fractionation led to the isolation and characterisation of two pheophytins, pheophytin a (1) and 132-hydroxy pheophytin a (2). Both compounds inhibited the production of NF-κB with IC50 values in the low micromolar range, with an IC50 between 12.32 and 16.01 µM for compound 1 and 7.91-9.87 µM for compound 2. CONCLUSIONS: The two pheophytins isolated in this study inhibit the production of NF-κB, thus showing that the traditional anti-inflammatory use of Tagetes minuta can be proved through pharmacological assays. This contributes to understanding the anti-inflammatory activity of the Huacatay extracts and their use in the treatment of stomach and intestinal discomfort.

In vitro anti-diabetic effect of flavonoids and pheophytins from Allophylus cominia Sw. on the glucose uptake assays by HepG2, L6, 3T3-L1 and fat accumulation in 3T3-L1 adipocytes.

BACKGROUND AND PURPOSE: Based on ethno-botanical information collected from diabetic patients in Cuba and firstly reported inhibition of PTP1B and DPPIV enzymes activities, Allophylus cominia (A. cominia) was identified as possible source of new drugs that could be used for the treatment of type 2 diabetes mellitus (T2-DM). EXPERIMENTAL APPROACH: in this study, the activity of the characterised extracts from A. cominia was tested on the glucose uptake using HepG2 and L6 cells, 3T3-L1 fibroblasts and adipocytes as well as their effect on the fat accumulation using 3T3-L1 adipocytes. KEY RESULTS: on 2-NBDG glucose uptake assay using HepG2 and L6 cells, extracts from A. cominia enhanced insulin activity by increasing glucose uptake. On HepG2 cells Insulin EC50 of 93 ± 21nM decreased to 13 ± 2nM in the presence of the flavonoids mixture from A.cominia. In L6 cells, insulin also produced a concentration-dependent increase with an EC50 of 28.6 ± 0.7nM; EC50 decreased to 0.08 ± 0.02nM and 5 ± 0.9nM in the presence of 100µg/ml of flavonoids and pheophytins mixtures, respectively. In 3T3-L1 fibroblasts, insulin had an EC50 of >1000nM that decreased to 38 ± 4nM in the presence of the flavonoids extract. However, in adipocytes, insulin produced a significant concentration-dependent increase and an EC50 of 30 ± 8nM was a further confirmation of the insulin responsiveness of the adipocytes to the insulin. At 100µg/ml, flavonoids and pheophytins extracts decreased fat accumulation in 3T3-L1 adipocytes by two folds in comparison to the control differentiated cells (p < 0.05). The crude extract of A. cominia did not show any enhancement of 2-NBDG uptake by 3T3-L1 adipocytes in the presence or absence of 100nM insulin. In addition, in fully differentiated adipocytes, both extracts produced significant decrease in lipid droplets in the cells and no lipid accumulation were seen after withdrawal of the extracts from the cell growth medium. However, there was no effect of both extracts on total protein concentration in cells as well as on Glut-4 transporters. CONCLUSIONS AND IMPLICATIONS: the pharmacological effects of the extracts from A. cominia observed in experimental diabetic models were shown in this study. A. cominia is potentially a new candidate for the treatment and management of T2-DM.

Identification of chlorophyll molecules with peroxyl radical scavenger capacity in microalgae Phormidium autumnale using ultrasound-assisted extraction.

The identification of chlorophyll molecules with peroxyl radical scavenger capacity in microalgae Phormidium autumnale was determined. The ultrasound-assisted extraction was utilized for obtaining the chlorophyll compounds from biomass. A total of eleven molecules were separated in microalgae chlorophyll extract, with pheophytin a' (371µg·g-1) and chlorophyll a (159.3µg·g-1) as the major ones. The chlorophyll extract was shown to be a potent scavenger of peroxyl radical, being almost 200 times more potent than α-tocopherol. These facts suggest the microalgae Phormidium autumnale as potential source of bioactive tetrapyrrole compounds.

In vitro anti-diabetic activity of flavonoids and pheophytins from Allophylus cominia Sw . on PTP1B, DPPIV, alpha-glucosidase and alpha-amylase enzymes.

BACKGROUND: Ethno-botanical information from diabetic patients in Cuba led to the identification of Allophylus cominia as a possible source of new drugs for the treatment of type 2 diabetes mellitus (T2-DM). EXPERIMENTAL: Chemical characterization of the extracts from A. cominia was carried out using chromatographic and spectroscopic methods. The extracts were tested for their activity on PTP1B, DPPIV, α-glucosidase enzymes and α-amylase. RESULTS: The flavonoid rich fractions from A. cominia inhibited DPPIV enzyme (75.3±2.33%) at 30µg/ml and produced a concentration-dependent inhibition against DPPIV with a Ki value of 2.6µg/ml. At 30µg/ml, flavonoids and pheophytins extracts significantly inhibited PTP1B enzyme (100±2.6% and 68±1% respectively). The flavonoids, pheophytin A and pheophytin B fractions showed significant concentration-dependent inhibition against PTP1B with Ki values of 3µg/ml, 0.64µg/ml and 0.88µg/ml respectively. At 30µg/ml, the flavonoid fraction significantly inhibited α-glucosidase enzyme (86±0.3%) in a concentration-dependent pattern with a Ki value of 2µg/ml. None of the fractions showed significant effects on α-amylase. Fatty acids, tannins, pheophytins A and B, and a mixture of flavonoids were detected in the methanolic extract from A. cominia. The identified flavonoids were mearnsitrin, quercitrin, quercetin-3-alloside, and naringenin-7-glucoside. CONCLUSION: The pharmacological effects of the extracts from A. cominia earlier observed in experimental diabetic models was confirmed in this study. Thus a new drug or formulation for the treatment of T2-DM could be developed from A. cominia.

Pheophytin a isolated from the seagrass Syringodium isoetifolium plausibly blocks umuC proteins of select bacterial pathogens, in silico.

AIMS: This investigation is designed to evaluate the antibacterial efficiency of the noodle grass Syringodium isoetifolium, which is commonly found in the Indian coastal waters. Also, this study characterizes the active compound and predicts the mode of action in silico. METHODS AND RESULTS: Human pathogenic bacteria were treated with crude metabolites of S. isoetifolium. The potent fraction b was analysed by UV/VIS, Spectroscopy RP-HPLC, FT-IR, ESI-Mass and 1 H and 13 C NMRs and determined to be a hydrate of pheophytin a (C55 H74 N4 O6 ). The isolated compound Pheo had MIC values of 6·2 ± 0·7 (Salmonella typhi) and 12·5 ± 0·8 (Escherichia coli and Pseudomonas aeruginosa) µg ml-1 . Molecular docking studies of the compound were done to find the binding sites on the pathogens using a Molegro Virtual Docker platform. Pheo targets umuC proteins by binding compactly to five amino acid residues with interaction energy of -3·66 and a Moldock score of -160·175. CONCLUSIONS: Hence, we conclude that pheophytin a, besides being an accessory photosynthetic pigment, also has proven to be antibacterial against human pathogens. Lesser MIC values with definite binding sites predicted in silico are suggestive of a precise of action for this compound. SIGNIFICANCE AND IMPACT OF THE STUDY: Easy extraction methods of the active compound that has a definite target render this under-explored seagrass a good source of antibacterial compound against human pathogenic bacteria. This learning may favour more researches in this unexplored area to build up Pheo-based natural products as antibiotic therapies.

Lipoxygenase inhibitors derived from marine macroalgae.

The solvent extracts from the algae Sargassum thunbergii (Sargassaceae) and Odonthalia corymbifera (Rhodomelaceae) were subjected to soybean lipoxygenase inhibitory screening. Two hydrophobic inhibitors were obtained from the extracts of S. thunbergii through inhibitory assay-guided fractionation. The inhibitors were identified as known exo-methylenic alkapolyenes (6Z,9Z,12Z,15Z)-1,6,9,12,15-henicosapentaene (1) and (6Z,9Z,12Z,15Z,18Z)-1,6,9,12,15,18-henicosahexaene (2). The alkapolyenes 1 and 2 showed higher inhibitory activity than the known inhibitor nordihydroguaiaretic acid (NDGA). Pheophytin a (3) was obtained from the extract of O. corymbifera. The inhibitor 3 also showed higher inhibitory activity than NDGA. This is the first report on lipoxygenase inhibition of exo-methylenic alkapolyenes and a chlorophyll a-related substance.

[Chemical Constituents of Seaweed Sargassum naozhouense].

OBJECTIVE: To investigate the chemical constituents in the seaweed Sargassum naozhouense collected from the sea around Zhanjiang. METHODS: The compounds were isolated and purified by various chromatographic techniques including silica gel chromatography, Sephadex LH-20 gel chromatography as well as preparative thin layer chromatography, and their structures were identified by spectral analysis. RESULTS: Ten compounds were isolated and identified as 1-O-hexadecanoyl glycerol (1), pheophytin a(2), ß-sitosterol (3), mannitol (4), uracil (5), thymine(6),p-hydroxybenzoic acid(7) 3,4-dihydroxybenzoic acid (8) 4-hydroxyphthalide (9), and 2'-de-cxythymidine( 10). CONCLUSION: All the compounds are isolated from the seaweed Sargassum naozhouense for the first time.

Pheophytin a and chlorophyll a identified from environmentally friendly cultivation of green pepper enhance interleukin-2 and interferon-γ in Peyer's patches ex vivo.

The oral consumption of capsicum has been reported to increase interleukin (IL)-2 and interferon (IFN)-γ production in Peyer's patches (PP); however, the active components responsible for these effects have not been completely identified. The beneficial biological effects of green peppers cultivated under environmentally friendly farming conditions (ECP), without the use of chemical pesticides, have rarely been compared with those of green peppers cultivated under conventional farming conditions (CCP). Oral administration of ECP extract significantly induced the production of IL-2 and IFN-γ in concanavalin A-treated cells from PP ex vivo; their levels were much higher than those in the CCP extract-treated group. A comparative analysis of the HPLC profiles indicated a 1.7-fold increase of a peak, named EF-1, at 415 nm in the ECP extract. The major component of EF-1 was identified as pheophytin a, which is a chlorophyll a molecule lacking a central Mg(2+) ion, as determined from NMR data. Intake of pheophytin a and chlorophyll a significantly increased IL-2 and IFN-γ production, and the percentage of IL-2- and IFN-γ-producing CD4+ T-cells in PP. Taken together, our data suggest that ECPs produce a higher content of pheophytin a than CCPs, and pheophytin a and chlorophyll a are immune-modulating components in green vegetables.

Chemical constituents from the leaves of Michelia alba.

(-)-N-Formylanonaine (1), (-)-oliveroline (2), (+)-nornuciferine (3), lysicamine (4), (+)-cyperone (5), (+)-epi-yangambin (6), ficaprenol-10 (7), pheophytin a (8), aristophyll C (9) and michephyll A (10) were isolated from the leaves of Michelia alba DC (Magnoliaceae). Among them, 10 is a new compound. The structures of these compounds were characterised and identified by spectral analyses. We have also presented the antioxidation activity of 10.

Bioactivity-guided screening identifies pheophytin a as a potent anti-hepatitis C virus compound from Lonicera hypoglauca Miq.

Chronic hepatitis C virus (HCV) infection is a worldwide public issue. In this study, we performed bioactivity-guided screening of the Lonicera hypoglauca Miq. crude extracts to find for naturally chemical entities with anti-HCV activity. Pheophytin a was identified from the ethanol-soluble fraction of L. hypoglauca that elicited dose-dependent inhibition of HCV viral proteins and RNA expression in both replicon cells and cell culture infectious system. Computational modeling revealed that pheophytin a can bind to the active site of HCV-NS3, suggesting that NS3 is a potent molecular target of pheophytin a. Biochemical analysis further revealed that pheophytin a inhibited NS3 serine protease activity with IC(50)=0.89 microM. Notably, pheophytin a and IFNalpha-2a elicited synergistic anti-HCV activity in replicon cells with no significant cytotoxicity. This study thereby demonstrates for the first time that pheophytin a is a potent HCV-NS3 protease inhibitor and offers insight for development of novel anti-HCV regimens.

Chemical constiuents from Richardia grandiflora (Cham. & Schltdl.) Steud. (Rubiaceae) / Constituintes químicos de Richardia grandiflora (Cham. & Schltdl.) Steud. (Rubiaceae)

Amongst the different forms of therapy to prevent and cure illnesses, plants have been, undoubtedly, the most utilized ones since the beginning of mankind. Brazil has a great diversity on plants that possess non-researched medicinal potential and are promising sources of therapeutic and pharmacological innovations. The Rubiaceae family is considered the biggest one of the order Gentianales, presenting around 637 genera and 10,700 species. Richardia grandiflora (Cham. & Schltdl.) Steud., known popularly as "ervanço", "poaia" or "ipeca-mirim", has ethnopharmacological indications to use as decoction against hemorrhoids and as vermifuge. Aiming at contributing to the chemotaxonomic study of the family Rubiaceae and considering the absence of data in literature about the chemical constitution of the species Richardia grandiflora, the latter was submitted to a phytochemical study to isolate its chemical constituents, through usual chromatographic methods, and after identifying them by means of spectroscopic methods such as ÕH and 13C NMR, with the add of two-dimensional techniques, besides comparison with literature data. Five constituents were isolated through this first phytochemical study with R. grandiflora: a mixture of the steroids beta-sitosterol and stigmasterol, o-hydroxy-benzoic acid, m-methoxy-p-hydroxy-benzoic acid and phaeophitin A, all of them isolated for the first time from the genus Richardia.

Dentre as diversas formas de terapia para a prevenção e cura de doenças, as plantas foram, indubitavelmente, as mais amplamente utilizadas desde o início da humanidade. O Brasil tem grande diversidade de plantas com potenciais medicinais, ainda não pesquisados, e que são promissoras fontes de inovações terapêuticas e farmacológicas. A família Rubiaceae, considerada a maior da ordem Gentianales, possui cerca de 637 gêneros e 10.700 espécies. Richardia grandiflora (Cham. & Schltdl.) Steud., conhecida popularmente como ervanço, poaia ou ipeca-mirim, tem indicações etnofarmacológicas para uso contra hemorróidas e como vermífugo na forma de decocto. Visando a contribuir com o estudo quimiotaxonômico da família Rubiaceae e tendo em vista a ausência de dados na literatura acerca da constituição química de Richardia grandiflora, esta foi submetida a um estudo fitoquímico para o isolamento de seus constituintes químicos, através dos métodos cromatográficos usuais, e posterior identificação estrutural dos mesmos, utilizando-se os métodos espectroscópicos de RMN ÕH e 13C uni e bidimensionais, além de comparações com modelos da literatura. Deste estudo pioneiro com R. grandiflora foram isolados e identificados cinco constituintes: uma mistura dos esteróides beta-sitosterol e estigmasterol, o ácido o-hidroxibenzóico, o ácido m-metoxi-p-hidroxi-benzóico e a feofitina A, todos inéditos no gênero Richardia.

Separation and determination of minor photosynthetic pigments by reversed-phase HPLC with minimal alteration of chlorophylls.

Reversed-phase HPLC conditions for separation of chlorophyll (Chl) a, Chl a' (the C132-epimer of Chl a), pheophytin (Pheo) a (the primary electron acceptor of photosystem (PS) II), and phylloquinone (PhQ) (the secondary electron acceptor of PS 1), have been developed. Pigment extraction conditions were optimized in terms of pigment alteration and extraction efficiency. Pigment composition analysis of light-harvesting complex II, which would not contain Chl a' nor Pheo a, showed the Chl a'/Chl a ratio of 3-4 x 10(-4) and the Pheo a/Chl a ratio of 4-5 x 10(-4), showing that the conditions developed here were sufficiently inert for Chl analysis. Preliminary analysis of thylakoid membranes with this analytical system gave the PhQ/Chl a' ratio of 0.58 +/- 0.03 (n = 4), in line with the stoichiometry of one molecule of Chl a' per PS I.

Normal-phase HPLC separation of possible biosynthetic intermediates of pheophytin a and chlorophyll a'.

Normal-phase HPLC conditions have been developed for separating the C17(3) isoprenoid isomers, which are expected to be formed as biosynthetic intermediates of chlorophyll (Chl) a, Chl a' (C13(2)-epimer of Chl a), pheophytin (Pheo) a and protochlorophyll (PChl). The application of these conditions to pigment composition analysis of greening etiolated barley leaves allowed us to detect, for the first time, the C17(3) isomers of Chl a', a possible constituent of the primary electron donor of photosystem (PS) I, P700, and those of Pheo a, the primary electron acceptor of PS II, in the very early stage of greening. The C17(3) isomer distribution patterns were approximately the same between Chl a and Chl a', but significantly different between Pheo a and Chl a', probably reflecting the similarity and difference, respectively, in the biosynthetic pathways of these pigment pairs.

Identification and antioxidant activity of several pigments from the residual green tea (Camellia sinensis) after hot water extraction.

Antioxidant activity of green tea extract or tea-derived polyphenols has been extensively studied. However, antioxidant activity in the non-polyphenolic fraction of green tea has been poorly analyzed. In the present study, we analyzed the antioxidant activity of the non-polyphenolic fraction of the residual green tea (Camellia sinensis) after hot water extraction using the aluminum chloride method. The non-polyphenolic fraction of residual green tea caused a significant suppression against hydroperoxide generation from oxidized linoleic acid in a dose-dependent manner. When the concentrate of the non-polyphenolic fraction was applied to a silica gel TLC plate and developed, six color spots were observed, which were considered to be chlorophylls a and b, pheophytins a and b, carotenoids, such as beta-carotene and lutein according to their specific colors, Rf values of silica gel TLC and spectrophotometric properties. Among these pigments, pheophytins a and b showed relatively abundant amounts, and the second major group of the pigment was chlorophylls a and b, and carotenoids such as beta-carotene and lutein indicated lower concentrations. Although all these pigments exhibited significant antioxidant activities, the ranks of suppressive activity against hydroperoxide generation were chlorophyll a > lutein > pheophytin a > chlorophyll b > beta-carotene > pheophytin b. These results suggest that the non-polyphenolic fraction of residual green tea has a potent suppressive activity against hydroperoxide generation from oxidized linoleic acid, which is derived from the antioxidant activities of chlorophylls a and b, pheophytins a and b, beta-carotene and lutein. This finding also implies that the combined intake of polyphenols in water-soluble fraction and antioxidative pigments in the non-polyphenolic fraction of green tea will be more efficient to prevent life style-related chronic diseases.

Potent suppressive activity of pheophytin a and b from the non-polyphenolic fraction of green tea (Camellia sinensis) against tumor promotion in mouse skin.

Chlorophyll-related compounds pheophytin a and b have been recently identified as antigenotoxic substances in the non-polyphenolic fraction of green tea (Camellia sinensis), which suppressed umu C gene expression in tester bacteria induced by various genotoxins (Okai and Higashi-Okai, Cancer Lett. 118 (1997) 117-123). In the present study, the authors analyzed in vivo and in vitro effects of pheophytin a and b from the non-polyphenolic fraction of green tea on tumor promotion in mouse skin as follows. (1) When pheophytin a and b from green tea were topically applied prior to each treatment with a tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) on BALB/c mouse skin initiated by 7,12 dimethylbenz[a]anthracene (DMBA), they caused suppression in a dose-dependent fashion against skin tumorigenesis. (2) Pheophytin a and b exhibited significant suppressions against TPA-induced inflammatory reaction, such as edema formation, in BALB/c mouse ear skin in a dose-dependent manner. (3) Pheophytin a and b from green tea showed inhibitory effects against early induction of ornithine decarboxylase (ODC) in BALB/c mouse skin fibroblasts caused by TPA. These results suggest that pheophytin a and b from the non-polyphenolic fraction have potent suppressive activities against tumor promotion in mouse skin.

Potent anti-inflammatory activity of pheophytin a derived from edible green alga, Enteromorpha prolifera (Sujiao-nori).

Recently, a chlorophyll-related compound, pheophytin a, has been identified from an edible green alga, Enteromorpha prolifera (Sujiao-nori in Japanese) as a potent suppressive substance against genotoxin-induced umu C gene expression in a tester bacteria (Okai and Higashi-Okai, 1997, J. Sci. Food Agricul. 71, 531-535). In the present study, anti-inflammatory effects of pheophytin a from Enteromorpha prolifera have been analyzed using in vitro and in vivo experiments. 1. Pheophytin a suppressed the production of superoxide anion (O2-) in mouse macrophages induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) using the cytochrome C reduction method. 2. Pheophytin a caused a suppressive effect against formyl-Met-Leu-Phe, (FMLP)-induced chemotaxis of human polymorphonuclear leukocytes (PMNs) in Boyden's chamber experiment. 3. Pheophytin a exhibited a significant suppression against TPA-induced inflammatory reaction such as edema formation in BALB/c mouse ear. These results suggest that pheophytin a from Enteromorpha prolifera has a potent anti-inflammatory activity.

Phaeophytins from a cell suspension culture of the liverwort Plagiochila ovalifolia.

A suspension culture of the liverwort Plagiochila ovalifolia was established from callus tissue induced by culturing spores. From the cultured cells, four phaeophytins were isolated as major components and their structures determined by spectroscopic methods. The phaeophytin derivatives showed antibacterial activity. A major sesquiterpenoid, ovalifoliene, found in the mother plant, was detected in the cultures by GC-mass spectrometry.

Separation of mono- and divinyl chlorophyll species by high-performance liquid chromatography using an octadecyl polyvinyl alcohol polymer column.

Most of the chlorophylls and their related compounds from nonesterified chlorophyllide to esterified pheophytin were separated by high- performance liquid chromatography using a wide pore, C(18) polyvinyl alcohol polymer column with an elution using a binary gradient starting from a buffered mobile phase. The high selectivity of this system enabled not only the separation of common chlorophyll species but also the resolution of structurally similar compounds such as mono- and divinyl chlorophyllide and pheophorbide species which usually coelute on monomeric bonded phases. The method is successfully applied to analyses of the pigments extracted from green and etiolated tissues of higher plants and photosynthetic bacterial cells.

D1-D2-cytochrome b559 complex from the aquatic plant Spirodela oligorrhiza: correlation between complex integrity, spectroscopic properties, photochemical activity, and pigment composition.

A D1-D2-cyt b559 complex with about four attached chlorophylls and two pheophytins has been isolated from photosystem II of the aquatic plant Spirodela oligorrhiza and used for studying the detergent-induced changes in spectroscopic properties and photochemical activity. Spectral analyses (absorption, CD, and fluorescence) of D1-D2-cyt b559 preparations that were incubated with different concentrations of the detergent Triton X-100 indicate two forms of the D1-D2-cyt b559 complexes. One of them is photochemically active and has an absorption maximum at 676 nm, weak fluorescence at 685 nm, and a strong CD signal. The other is photochemically inactive, with an absorption maximum at 670 nm, strong fluorescence at 679 nm, and much weaker CD. The relative concentrations of the two forms determine the overall spectra of the D1-D2-cyt b559 preparation and can be deduced from the wavelength of the lowest energy absorption band: preparations having maximum absorption at 674, 672, or 670.5 nm have approximately 20, 60, or 85% inactive complexes. The active form contains two chlorophylls with maximum absorption at 679 nm and CD signals at 679 (+) and 669 nm (-). These chlorophylls make a special pair that is identified as the primary electron donor P-680. The calculated separation between the centers of these two pigments (using an extended version of the exciton theory) is about 10 A, the pigments' molecular planes are tilted by about 20 degrees, and their N1-N3 axes are rotated by 150 degrees relative to each other. The other two chlorophylls and one of the two pheophytins in the D1-D2-cyt b559 complex have their maximum absorption at 672 nm, while the maximum absorption of the photochemically active pheophytin is probably at 672-676 nm. During incubation with Triton X-100, the photochemically active complex is transformed into an inactive form with first-order kinetics. In the inactive form the maximum absorption of the 679 nm absorbing Chls is blue-shifted to 669 nm. The first-order decay of the photochemical activity suggests that the isolated D1-D2-cyt b559 complex is stable as an aggregate but becomes unstable on dissociation into individual D1-D2-cyt b559 units.