Rogers E. Harry-O'kuru

Synthesis and characteristics of polyhydroxy triglycerides from milkweed oil

The milkweed family Asclepiadaceae comprises many genera including the genus Asclepias syriaca, otherwise known as the common milkweed. This plant had been considered a nuisance and serious efforts made toward its eradication. However, milkweed has become an industrial crop of growing significance on account of market demand for its hypoallergenic floss in pillows, comforters and other industrial uses. Processing of milkweed pods gives three product streams of floss, seed and pod hulls. The seed contains about 25% by weight of very highly unsaturated oil with some unusual fatty acids. The objective of this study was to generate value-added products from milkweed oil. To achieve this, the triglycerides of A. syriaca seed were oxidized to the polyoxirane and polyhydroxy triglyceride derivatives by means of an in situ peroxy acid method. The epoxy triglycerides produced exhibited high stability and highly viscous behavior, whereas the polyhydroxy triglycerides showed additional unusually stable emulsifying properties for oil in water emulsions.

Milkweed seedmeal: a control for Meloidogyne chitwoodi on potatoes

Abstract Milkweed (Asclepias) is a new crop being produced for its fiber in pillows and comforters. Cardiac glycosides (cardenolides), are endemic in milkweed and may hinder utilization of its seed as an animal feed. In an ongoing effort to develop new coproducts for milkweed fiber, we found that the defatted seedmeal is an effective nematicide and pesticide for army worms. A procedure for separating the cardenolides from milkweed seedmeal has also been developed.

Cardenolide analysis of cold-pressed milkweed oil

Abstract A spectrophotometric procedure was developed to detect and quantify cardenolide content of oil extracted from the seed of the common milkweed (Asclepias syriaca). The technique exploits the reaction of 2,2′,4,4′-tetranitrobiphenyl (TNBP) with cardenolides to form colored complexes in the presence of NaOH. The complex has an absorbance maximum at 620 nm with intensity maximum usually attained in 40 min after NaOH addition. Digitoxin, a known cardiac glycoside, was employed in generating standard calibration curves for the analysis. Absorbance spectra of A. syriaca cold-pressed and petroleum ether extracted oil samples as well as food-grade commercial vegetable oils, were compared to those of standards in order to detect and estimate their cardenolide content. No cardenolides were found in A. syriaca oil at detection limits of less than 1 ppm.

Elimination of interference from water in KBr disk FT-IR spectra of solid biomaterials by chemometrics solved with kinetic modeling

Infrared analysis of proteins and polysaccharides by the well known KBr disk technique is notoriously frustrated and defeated by absorbed water interference in the important amide and hydroxyl regions of spectra. This interference has too often been overlooked or ignored even when the resulting distortion is critical or even fatal, as in quantitative analyses of protein secondary structure, because the water has been impossible to measure or eliminate. Therefore, a new chemometric method was devised that corrects spectra of materials in KBr disks by mathematically eliminating the water interference. A new concept termed the Beer-Lambert law absorbance ratio (R-matrix) model was augmented with water concentration ratios computed via an exponential decay kinetic model of the water absorption process in KBr, which rendered the otherwise indeterminate system of linear equations determinate and thus possible to solve in a formal analytic manner. Consequently, the heretofore baffling KBr water elimination problem is now solved once and for all. Using the new formal solution, efforts to eliminate water interference from KBr disks in research will be defeated no longer. Resulting spectra of protein were much more accurate than attenuated total reflection (ATR) spectra corrected using the well-accepted Advanced ATR Correction Algorithm.

Processing Scale-Up of Sicklepod (Senna obtusifolia L.) Seed

Sicklepod (Senna obtusifolia L.) is an invasive weed species especially of soybean and other field crops in the southeastern United States. The seeds contain a small amount (5-7%) of a highly colored fat as well as various phenolics, proteins, and galactomannans. The color of sicklepod seed oil is such that the presence of a small amount of the weed seed in a soybean crush lowers the quality of the soybean oil. Sicklepod is very prolific, and even volunteer stands yield >1000 lb of seed per acre, and prudence calls for tapping the potential of this weed as an alternative economic crop in the affected region. Pursuant to this, we have shown in laboratory-scale work the feasibility of separating the components of sicklepod seed. However, at kilogram and higher processing quantities, difficulties arise leading to modification of the earlier approach in order to efficiently separate components of the defatted seed meal. In a version for cleanly separating the proteins, the defatted meal was extracted with 0.5 M NaCl solution to remove globular proteins. Prolamins were extracted from the pellet left after salt extraction using 80% ethanol, and glutelins were then obtained in 0.1 N alkali from the residual solids left from ethanol treatment. In a pilot-scale version for water-soluble polysaccharides, the defatted meal was stirred with deionized water (DI) and centrifuged. The pooled centrifugates were heated to 92 degrees C (20-25 min), filtered, cooled to room temperature, and passed through a column of Amberlite XAD-4 to separate the polysaccharides from the anthraquinones. Senna obtusifolia L. is a one-stop-shop of a seed (from food components to medicinals).

Synthesis of Polyformate Esters of Vegetable Oils: Milkweed, Pennycress, and Soy

In a previous study of the characteristics of acyl derivatives of polyhydroxy milkweed oil (PHMWO), it was observed that the densities and viscosities of the respective derivatives decreased with increased chain length of the substituent acyl group. Thus from the polyhydroxy starting material, attenuation in viscosity of the derivatives relative to PHMWO was found in the order: PHMWO ≫ PAcMWE ≫ PBuMWE ≫ PPMWE (2332 : 1733 : 926.2 : 489.4 cSt, resp., at 40°C), where PAcMWE, PBuMWE, and PPMWE were the polyacetyl, polybutyroyl, and polypentanoyl ester derivatives, respectively. In an analogous manner, the densities also decreased as the chain length increased although not as precipitously compared to the viscosity drop. By inference, derivatives of vegetable oils with short chain length substituents on the triglyceride would be attractive in lubricant applications in view of their higher densities and possibly higher viscosity indices. Pursuant to this, we have explored the syntheses of formyl esters of three vegetable oils in order to examine the optimal density, viscosity, and related physical characteristics in relation to their suitability as lubricant candidates. In the absence of ready availability of formic anhydride, we opted to employ the epoxidized vegetable oils as substrates for formyl ester generation using glacial formic acid. The epoxy ring-opening process was smooth but was apparently followed by a simultaneous condensation reaction of the putative α-hydroxy formyl intermediate to yield vicinal diformyl esters from the oxirane. All three polyformyl esters milkweed, soy, and pennycress derivatives exhibited low coefficient of friction and a correspondingly much lower wear scar in the 4-ball antiwear test compared to the longer chain acyl analogues earlier studied.