The conjugation of phytosterols (PSs) with fatty acids results in producing phytosterol esters (PSEs) characterized with enhanced lipophilicity and improved functional properties of major interest in food and nutraceutical applications. The use of immobilized lipases to catalyze direct transesterification reactions between PSs and plant oils to form PSEs as a green alternative to conventional chemical production methods has attracted interest during the last two decades. The low solubility of PSs in common plant oil triglycerides, typically below 3% at ambient temperatures, remains the main challenge for bringing lipase-catalyzed direct transesterification reactions of PSs and oil triglycerides to commercial scales. This study focuses on the enzymatic synthesis of PSEs starting from solubilized PSs at concentrations of up to 30% wt./wt. of oil mixtures comprising fatty acid ethyl esters (FAEEs), monoglycerides (MGs), diglycerides (DGs) and triglycerides (TGs) as a homogeneous medium for the direct transesterification reaction. The results of this study show for the first time that the addition of FAEEs into the reaction medium results in altering of the substrate preference of the enzyme making MGs as the favorite fatty acyl group donors for PSs amongst all other fatty acyl donors present in the reaction system. The proposed new enzymatic route allows starting with high concentrations of solubilized PSs making the direct transesterification of oil glycerides attractive for production of PSEs at industrials scales.

The seeds of cultivated peanut, Arachis hypogaea, are an agronomically important crop produced for human nutrition, oilseed and feed stock. Peanut seed is the single most expensive variable input cost and thus producers require seed with excellence performance in terms of germination efficiency. During the maturation process, triglycerides are stored in oil bodies as an energy resource during germination and seedling development. The stability of oil body membranes is essential for nutrient mobilization during germination. This study focused on evaluating the phytosterol composition in seed components including the kernel, embryo (heart), and seed coat or skin. Samples of different maturity classes were analyzed for macronutrient and phytosterol content. The three most abundant phytosterols, β-sitosterol, campesterol, and stigmasterol, comprised 82.29%, 86.39%, and 94.25% of seed hearts, kernels, and seed coats, respectively. Stigmasterol concentration was highest in the seed kernel providing an excellent source of this sterol known to have beneficial effects on human health. Peanut hearts contained the highest concentration of sterols by mass potentially providing protection and resources for the developing seedling. The amount of α-tocopherol increases in peanut hearts during the maturation process providing protection from temperature stress and stability required for seedling vigor. These results suggest that phytosterols may play a significant role in the performance of seeds and provides a possible explanation for the poor germination efficiency of immature seeds.

Hypercholesterolemia accelerates atherosclerosis, and extensive research has been undertaken to ameliorate this abnormality. Plant sterols have been shown to inhibit cholesterol absorption and lower plasma cholesterol level since the 1950s. This ingredient has recently been reappraised as a food additive that can be taken daily in a preclinical period to prevent hypercholesterolemia, considering that cardiovascular-related diseases are the top cause of death globally even with clinical interventions. Intestinal cholesterol handling is still elusive, making it difficult to clarify the mechanism for plant sterol-mediated inhibition. Notably, although the small intestine absorbs cholesterol, it is also the organ that excretes it abundantly, via trans-intestinal cholesterol efflux (TICE). In this review, we show a model where the brush border membrane (BBM) of intestinal epithelial cells stands as the dividing ridge for cholesterol fluxes, making cholesterol absorption and TICE inversely correlated. With this model, we tried to explain the plant sterol-mediated inhibitory mechanism. As well as cholesterol, plant sterols diffuse into the BBM but are effluxed back to the lumen rapidly. We propose that repeated plant sterol shuttling between the BBM and lumen promotes cholesterol efflux, and plant sterol in the BBM may disturb the trafficking machineries that transport cholesterol to the cell interior.

Chitosan treatment results in significantly lower serum LDL cholesterol concentrations. To assess the working mechanism of chitosan, we measured serum surrogate markers of cholesterol absorption (campesterol, sitosterol, cholestanol), synthesis (lathosterol, lanosterol, desmosterol), and degradation to bile acids (7α-hydroxy-cholesterol, 27-hydroxy-cholesterol) corrected for cholesterol concentration (R_sterols). Over 12 weeks, 116 obese subjects (BMI 31.7, range 28.1 – 38.9 kg/m²) were studied under chitosan (n=61) and placebo treatment (n=55). The participants were briefly educated regarding improvement of nutrition quality and energy expenditure. Daily chitosan intake was 3200 mg. Serum LDL cholesterol concentration decreased significantly more (P=0.0252) under chitosan (-8.67 ± 18.18 mg/dl, 5.6%) than under placebo treatment (-1.00 ± 24.22 mg/dl, 0.9%). This reduction was not associated with the expected greater decreases in markers of cholesterol absorption under chitosan treatment. Also, increase in markers of cholesterol synthesis and bile acid synthesis under chitosan treatment was not any greater than under placebo treatment. In conclusion, a significant selective reduction of serum LDL cholesterol under chitosan treatment is neither associated with a reduction of serum surrogate markers of cholesterol absorption nor with an increases of markers for cholesterol and bile acid synthesis.