Metabolite Profiling and Transcriptome Analyses Provide Insight Into Phenolic and Flavonoid Biosynthesis in the Nutshell of Macadamia Ternifolia

Macadamia ternifolia is a dynamic oil-producing nut crop in the world. However, the nutshell is frequently considered as a low-quality material. Further, its metabolic profile is still uncharacterized. In order to explore the industrial significance of the nutshell, this study performed metabolic and transcriptomic analyses at various developmental stages of the nutshell. The qualitative and quantitative metabolic data analysis identified 596 metabolic substances including several species of phenolic acids, flavonoids, lipids, organic acids, amino acids and derivatives, nucleotides and derivatives, alkaloids, lignans, coumarins, terpenoids, tannins, and others. However, phenolic acids and flavonoids were predominant, and their abundance levels were significantly altered across various developmental stages of the nutshell. Comparative transcriptome analysis revealed that the expression patterns of phenolic acid and flavonoid pathway related genes were significantly changed during the nutshell growth. In particular, the expression of phenylalanine ammonia-lyase, C4H, 4CL, CHS, CHI, F3H, and FLS had dynamic differences at the various developmental stages of the nutshell. Our integrative metabolomic and transcriptomic analyses identified the key metabolic substances and their abundance levels. We further discussed the regulatory mechanism of phenolic and flavonoid biosynthesis in the nutshell of M. ternifolia. Our results provide new insights into the biological profiles of the nutshell of M. ternifolia and help to elucidate the molecular mechanisms of phenolic and flavonoid biosynthesis in the nutshell of M. ternifolia.

Chemistry and Functionality of Cold-Pressed Macadamia Nut Oil

The rising trend in the consumption of healthy, safe, and functional foods has motivated studies on cold-pressed specialty oils, including macadamia nut oil. Cold-pressed macadamia nut oil (CPMO) is given preference by consumers over solvent extracted and refined oil because of its exceptional quality attributes and safety. This review contains a detailed presentation of the chemical properties, health benefits, and applications of CPMO. The monounsaturated fatty acids (oleic acid and palmitoleic acid) rich oil also contains a significant concentration of bioactive phytochemicals including, β-sitosterol, α-tocopherol, α-tocotrienols, ρ-hydroxybenzoic acid, and caffeic acid. Moreover, the oil has good oxidative stability. The highlighted properties offer CPMO health benefits related to the prevention of cardiovascular diseases, diabetes, cancer, high blood pressure, and neurodegenerative diseases. The fatty acid composition of CPMO allows for its diverse application in the food, cosmetic, nutraceutical, and pharmaceutical industries.