In recent years, deep eutectic systems (DES) emerged as novel vehicles for facilitating the transdermal delivery of various drugs, including polysaccharides, proteins, insulin, vaccine, nanoparticles, and herb extracts. The objective of this study is to conduct a comprehensive review of the application of DES to transdermal drug delivery, based on previous work and the reported references. Following a brief overview, the roles of DES in TDDS, the modes of action, as well as the structure–activity relationship of DES are discussed. Particularly, the skin permeation of active macromolecules and rigid nanoparticles, which are the defining characteristics of DES, are extensively discussed. The objective is to provide a comprehensive understanding of the current investigation and development of DES-based transdermal delivery systems, as well as a framework for the construction of novel DES-TDDS in the future.

The high background value of cadmium (Cd) in the Panax notoginseng planting soil is the main reason for the Cd content in P. notoginseng exceeding the limit standards. The main goal of this study was to reveal the mechanism by which potassium (K) reduces Cd accumulation in P. notoginseng from the perspective of the influences of soil microbial communities on soil pH, total organic matter (TOM) and cation exchange capacity (CEC). Pot experiments were conducted to study the effects of different types and amounts of applied K on the Cd content in P. notoginseng, and on the soil pH, TOM, CEC, and bioavailable Cd (bio-Cd) content in soil. Field experiments were conducted to study the effects of K₂SO₄ fertilizer on the microbial community, and its correlations with the soil pH, TOM and CEC were analyzed. A moderate application of K₂SO₄ (0.6 g⋅kg^–1) was found to be the most optimal treatment for the reduction of Cd in the pot experiments. The field experiments proved that K fertilizer (K₂SO₄) alleviated the decreases in pH, TOM and CEC, and reduced the content of bio-Cd in the soil. The application of K fertilizer inhibited the growth of Acidobacteria, but the abundances of Mortierellomycota, Proteobacteria and Bacteroidetes were promoted. The relative abundances of Acidobacteria and Proteobacteria in the soil bacteria exhibited significant negative and positive correlations with pH and CEC, respectively. In contrast, the relative abundance of Mortierellomycota was found to be positively correlated with the pH, TOM and CEC. The bio-Cd content was also found to be positively correlated with the relative abundance of Acidobacteriia but negatively correlated with the relative abundances of Proteobacteria and Mortierellomycota. The application of K fertilizer inhibited the abundance of Acidobacteria, which alleviated the acidification of the soil pH and CEC, and promoted increase in the abundances of Mortierellomycota, Proteobacteria and Bacteroidetes, which ultimately increased the soil TOM and CEC. Soil microorganisms were found to mitigated decreases in the soil pH, TOM, and CEC and reduced the bio-Cd content in the soil, which significantly reduced the accumulation of Cd in P. notoginseng.

The Panax notoginseng (P. notoginseng) stem leaf is rich in flavonoids. However, because of a lack of research on the flavonoid extraction process and functional development of P. notoginseng stem leaf, these parts are discarded as agricultural wastes. Therefore, in this study, we intend to optimize the extraction process and develop the skin-whitening functions of P. notoginseng stem leaf extracts. The extraction process of the stem and leaf of P. notoginseng flavonoid (SLPF) is optimized based on the Box–Behnken design (BBD) and the response surface methodology (RSM). The optimum extraction conditions of the SLPF are as follows: the extraction time, the ethanol concentration, the sodium dodecyl sulfate (SDS) content and the liquid material ratio (v/w, which are 52 min, 48.7%, 1.9%, and 20:1, respectively. Under the optimal extraction conditions, the average total SLPF content is 2.10%. The antioxidant activity and anti-deposition of melanin of mouse B16 cells of P. notoginseng stem leaf extracts are studied. The results indicate that the EC₅₀ values of reducing activity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activities, the superoxide anion removal ability, and the 2,2-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) free radical removal ability are 7.212, 2.893, 2.949, and 0.855 mg/mL, respectively. The extracts IC₅₀ values of the tyrosinase and melanin synthesis are 0.045 and 0.046 mg/mL, respectively. Therefore, the optimal processing technology for the SLPF obtained in this study not only increases its utilization rate, but also decreases material costs. The extracts from the P. notoginseng stem leaf may be developed as food or beauty products.

Excessive nitrogen (N) application and potassium (K) supplement deficiency is a common problem in Panax notoginseng cultivation. However, synergistic effects of lowering N and increasing K application on yield and quality of P. notoginseng have not been reported. Field experiments in two locations with different N and K combined application were conducted to study the effects on yield and quality. Then, the saponin accumulation mechanisms were explored by pot and hydroponic culture with 2- or 3-year-old seedlings. The investigation showed that 70% of P. notoginseng cultivation fields reached abundant levels of total nitrogen (TN) but had deficient levels of total potassium (TK), which may be detrimental to balance the N/K uptake of P. notoginseng. Moreover, the average biomass was 18.9 g, and P. notoginseng saponin (PNS) content was 6.95%; both were influenced by the N/K values of P. notoginseng. The field experiments indicated that compared to the conventional N and K application (N:K = 2:1), lowering N and increasing K application (N:K = 1:2) decreased root rot rate by 36.4–46.1% and increased survival rate, root biomass, and yield, as well as PNS content by 17.9–18.3, 5.7–32.9, 27.8–57.1, and 5–10%, respectively. The mechanism of lowering N and increasing K application on the PNS content improving was due to the decreasing of N/K value, which promoted photosynthesis, sugar accumulation, and the expression of saponin biosynthesis genes. Therefore, lowering N and increasing K application to the ratio of 1:2 would have great potential to improve the synergistic effect on yield and quality of P. notoginseng cultivation.