2-Hydroxy-1,4-naphthoquinone (Lawsone) as a Redox Catalyst for the Improvement of the Alkaline Pretreatment of Sugarcane Bagasse

Abstract

This study evaluated the use of a new redox catalyst (2-hydroxy-1,4-naphthoquinone, HNQ) in order to contribute to the preservation of the carbohydrate fraction and to increase delignification of sugarcane bagasse (SB) subjected to soda pretreatment, without inhibiting enzyme activity during saccharification. The effects of HNQ were compared to the well-known redox catalyst anthraquinone (AQ). A 25‑1 fractional design and a 22 central composite design were used for optimization of the soda-HNQ pretreatment of SB. The use of HNQ promoted preservation of 76.4% cellulose and 86.2% hemicelluloses, as well as 86.1% delignification of raw SB, showing a superior performance than AQ. The optimized pretreatment conditions were 150 °C, 60 min, 15% (w w–1) NaOH, 0.4% (w w–1) HNQ, and a liquid-to-solid ratio of 9.6 mL g–1. Saccharification of SB pretreated by soda-HNQ yielded higher overall glucose (74.0%) and xylose (74.3%) yields compared to SB pretreated by AQ (64.9% glucose, 67.3% xylose).

Recent Advances in the Synthesis of 2-Hydroxy-1,4-naphthoquinone (Lawsone) Derivatives

“…In the second step, ammonium thiocyanate and acid chlorides are combined at 70 °C under solvent-free conditions, leading to the generation of solid aroyl isothiocyanate derivatives 44a-e. Finally, the products from the first step react with the aroyl isothiocyanate derivatives in the presence of caffeine in [Bmim] + OHto yield the desired benzo[a] [1,3]oxazino [6,5c]phenazine derivatives 45a-j (Scheme 12). This methodology offers several advantages, including its user-friendly nature, excellent yields of the desired products, avoidance of toxic or hazardous catalysts, high chemo-and regioselectivity, and [3,4-c]phenazines 50a-j, which possess both biologically active benzophenazine and pyrazolophthalazine templates.…”

“…Mohebat and co-workers 41 successfully synthesized benzo[a] [1,3]oxazino [6,5-c]phenazine derivatives 45a-j using a one-pot, four-component sequential condensation reaction. In this environmentally friendly approach, caffeine was employed as a natural catalyst.…”

“…The use of caffeine as a catalyst adds to the environmentally benign nature of the approach. 41 Scheme 12 Synthesis of benzo[a] [1,3]oxazino [6,5-c]phenazine derivatives 45a-j…”

“…2-Hydroxy-1,4-naphthoquinone, also known as lawsone or hennotannic acid, is a naturally occurring naphthoquinone compound that has attracted significant interest in synthetic organic chemistry. [1][2][3] It is one of the simplest naturally occurring naphthoquinones and is primarily known for its presence in the leaves of the henna plant (Lawsonia inermis), where it imparts a red-orange dye. 4 Humans have utilized henna extracts containing lawsone for thousands of years as hair and skin dyes, highlighting its historical and cultural significance.…”

Alkali-Catalyzed Organosolv Pretreatment of Lignocellulose Enhances Enzymatic Hydrolysis and Results in Highly Antioxidative Lignin

“…The burgeoning challenges such as petroleum-derived energy shortage along with environmental degradation namely destruction of ecosystem, habitat eradication, and extinction of wildlife have paved the way for biobased products from lignocellulose biomass and believed to provide a sustainable solution for the current and future needs. , In the present bioeconomy, it is not feasible to obtain high-value products from lignocellulose at a large scale. In order to increase the efficiency, pretreatment of lignocellulose is critical, mainly to wane the recalcitrant complex structure …”