Fabian M. Dayrit

Structural analysis of carrageenan from farmed varieties of Philippine seaweed

Abstract Kappaphycus alvarezii, Eucheuma denticulatum and, more recently, Kappaphycus sp. ‘Sacol’ variety, are the carrageenan-containing red seaweeds currently farmed in the Philippines. The Kappaphycus sp. ‘Sacol’ variety is of particular interest to the Philippine seaweed industry because of its improved resistance to ‘ice-ice’ disease and its fast growing characteristics. Here we report on the detailed chemical analysis of the carrageenan from this species. The native and alkali-modified carrageenans from Kappaphycus sp. ‘Sacol’ variety were characterized by FT-IR, 1H and 13C NMR spectroscopy, and constituent sugar and methylation analyses and were compared to those from K. alvarezii, K. cottonii and Eucheuma denticulatum. The three Kappaphycus species contained predominantly κ-carrageenan with low levels of ι-carrageenan, methylated carrageenan and μ-precursor residues, while Eucheuma denticulatum contained predominantly ι-carrageenan with significant amounts of ν-precursor residues. Taxonomic classification of Kappaphycus species based on morphology has proved to be difficult because of their known plasticity. Molecular analysis using the rbcL sequence revealed that the Kappaphycus sp. ‘Sacol’ variety is most likely a form of K. cottonii.

Mutagens from roasted seeds of moringa oleifera

A number of biosynthetically and chemically related compounds were isolated from the roasted seeds of Moringa oleifera. The micronucleus test, an in vivo method, using albino mice as the test system, was used for monitoring the mutagenicity of the isolated compounds. Structure-activity correlation studies showed that 4(alpha-L-rhamnosyloxy)phenylacetonitrile, 4-hydroxyphenylacetontrile, and 4-hydroxyphenyl-acetamide exhibited mutagenic activity.

Analysis of Monoglycerides, Diglycerides, Sterols, and Free Fatty Acids in Coconut (Cocos nucifera L.) Oil by 31P NMR Spectroscopy

Phosphorus-31 nuclear magnetic resonance spectroscopy ( (31)P NMR) was used to differentiate virgin coconut oil (VCO) from refined, bleached, deodorized coconut oil (RCO). Monoglycerides (MGs), diglycerides (DGs), sterols, and free fatty acids (FFAs) in VCO and RCO were converted into dioxaphospholane derivatives and analyzed by (31)P NMR. On the average, 1-MG was found to be higher in VCO (0.027%) than RCO (0.019%). 2-MG was not detected in any of the samples down to a detection limit of 0.014%. On the average, total DGs were lower in VCO (1.55%) than RCO (4.10%). When plotted in terms of the ratio [1,2-DG/total DGs] versus total DGs, VCO and RCO samples grouped separately. Total sterols were higher in VCO (0.096%) compared with RCO (0.032%), and the FFA content was 8 times higher in VCO than RCO (0.127% vs 0.015%). FFA determination by (31)P NMR and titration gave comparable results. Principal components analysis shows that the 1,2-DG, 1,3-DG, and FFAs are the most important parameters for differentiating VCO from RCO.

Acylglucosyl sterols from Momordica charantia

Abstract A mixture of acylglucosylsterols was isolated from the green fruits of Momordica charantia (balsam pear or bitter gourd) and the structure elucidated by high field 1 H NMR, 13 C NMR, FTIR and mass spectrometry and chemical modification studies followed by spectral and chromatographic analysis. The major acylglucosyl sterol was 3- O -[6′- O -palmitoyl-β- d -glucosyl]-stigmasta-5,25(27)-diene while the minor component was 3- O -[6′- O -stearyl-β- d -glucosyl]-stigmasta-5,25(27)-diene. The isolation and structure elucidation of these acylglucosyl sterols are reported for the first time.

Development of an analytical method for 3-monochloropropane-1,2-diol in soy sauce using 4-heptanone as derivatizing agent

3-Monochloro-1,2-propane diol is a suspected carcinogen found in hydrolysed vegetable protein products such as soy sauce. A method is described for the analysis of 3-monochloro-1,2-propane diol in soy sauce by gas chromatography-mass spectrometry at a concentration range of 1–5000 ng g−1 using 4-heptanone as the derivatizing ketone and 3-monochloro-1,2-propane diol-d5 as the internal standard. The limit of detection for the method in the soy sauce matrix was 0.48 ng g−1 and the limit of quantification was 1.2 ng g−1.

Quality characteristics of virgin coconut oil: Comparisons with refined coconut oil

Virgin coconut oil (VCO) is a vegetable oil that is extracted from fresh coconut meat and is processed using only physical and other natural means. VCO was compared to refined, bleached, and deodorized coconut oil (RCO) using standard quality parameters, 31P nuclear magnetic resonance (NMR) spectroscopy, and headspace solid-phase micro-extraction/gas chromatography mass spectrometry (SPME/GCMS). VCO tends to have higher free fatty acids (FFAs), moisture, and volatile matter and lower peroxide value than RCO. However, the range of values overlap and no single standard parameter alone can be used to differentiate VCO from RCO. Using 31P NMR, VCO and RCO can be distinguished in terms of the total amount of diglycerides: VCO showed an average content (w/w %) of 1.55, whereas RCO gave an average of 4.10. There was no overlap in the values found for individual VCO and RCO samples. There are four common methods of producing VCO: expeller (EXP), centrifuge (CEN), and fermentation with and without heat. VCO products prepared using these four methods could not be differentiated using standard quality parameters. Sensory analysis showed that VCO produced by fermentation (with and without heat) could be distinguished from those produced using the EXP and CEN methods; this sensory differentiation correlated with the higher levels of acetic acid and octanoic acid in the VCO produced by fermentation. Studies on physicochemical deterioration of VCO showed that VCO is stable to chemical and photochemical oxidation and hydrolysis. VCO is most susceptible to microbial attack, which leads to the formation of various organic acids, in particular, lactic acid. However, at moisture levels below 0.06 %, microbial action is significantly lessened.

Trace organic chemical pollutants from the lake waters of San Pablo City, Philippines by targeted and non-targeted analysis

More than half of the freshwater lakes in the Philippines are small with surface areas of <2 km2. The dynamics in these lakes are different from those in the bigger lakes. This study was conducted to determine the organic pollutants and their sources in three of the seven lakes of San Pablo City in Laguna, Philippines: lakes Palakpakin, Sampaloc, and Pandin. Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid Chromatography - Tandem Mass Spectrometry (LC-MS/MS) were used in the targeted and non-targeted analysis of the lake water samples. The three lakes are all volcanic crater lakes but are exposed to different anthropogenic activities, which includes domestic activities, livelihood (farming and aquaculture) and eco-tourism. Due to the presence of rice fields and fruit plantations, chlorpyrifos was detected in the three lakes while other pesticides like cypermethrin, picolinafen and quinoxyfen were additionally found in Lake Sampaloc, which is the biggest of the three lakes and located within the urbanized section of the city. Traces of different surfactants (linear alkylbenzene sulfonates, secondary alkyl sulfonates, alkyl sulfates, alkyl ether sulfates), biocide benzalkonium chloride, insect repellent diethyltoluamide, antibiotics (sulfadiazine and sulfamethoxazole), hypertension drug telmisartan, phosphate-based fire retardants, and artificial sweeteners (acesulfame, cyclamate, saccharin and sucralose) were detected in lakes Sampaloc and Palakpakin. The same surfactants, artificial sweeteners, insect repellant and phosphate-based fire retardants were also found in Lake Pandin, which is mainly used for eco-tourism activities like swimming and boating. The results of this study suggest that the organic pollutants present in the small lakes can be linked to the various human activities in the immediate lake environment. Because small lakes are more prone to environmental stresses, human activities in the said lakes must be regulated to ensure sustainable development.

Erratum to: Structural analysis of κ-carrageenan sulfated oligosaccharides by positive mode Nano-ESI-FTICR-MS and MS/MS by SORI-CID

The article by Jennifer T. Aguilan, Fabian M. Dayrit, Jinhua Zhang, Milady R. Niñonuevo and Carlito B. Lebrilla which was published in the January issue, Vol. 17, No. 1, pages 96–103, printed with an error in the title. The Greek letter “kappa” (κ) was mistakenly switched to a Greek letter “alpha” (α) in “-Carrageenan.” The actual title should have been “Structural Analysis of κ-Carrageenan Sulfated Oligosaccharides by Positive Mode Nano-ESI-FTICR-MS and MS/MS by SORI-CID” and is now published online in its corrected form on ScienceDirect. The publisher apologizes for the error.

Application of linear prediction and rapid acquisition to nuclear magnetic resonance

In pulse nuclear magnetic resonance (NMR) spectroscopy, data are obtained by perturbing the nucleus from its equilibrium position and acquiring the transient response. Fourier transformation is the preferred mode used in data processing of the signals due to its ability to compute the NMR spectrum rapidly. To obtain good signal-to-noise ratio, it is common practice to average many transients. To obtain good resolution, lengthier acquisition times are favored. For insensitive nuclei, where thousands of collected transients are necessary, this is a time-consuming procedure; especially if the nuclear relaxation time constant is in the order of seconds or minutes. A faster acquisition method is proposed. Using a modified NMR pulse sequence, the proposed method acquires signals more rapidly than by conventional acquisition methods; however, the signals are truncated. In processing truncated data; the shortcomings of the Fourier transform must be overcome by alternative spectral estimation methods. An alternative processing method - linear prediction (LP) - is used to reconstruct the spectrum from the incomplete time-domain magnetic resonance data. The LP methods application to truncated, fast acquisition of data is discussed in detail. This combination of methods is a novel way of acquiring and processing NMR spectroscopic data.