[reaction: see text] Oxidosqualene-lanosterol cyclases convert oxidosqualene to lanosterol in yeast and mammals. Site-saturated mutants' construction of Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase, at Trp232 exchanges against proteinogenic amino acids, and product profiles are shown. All mutants, except Lys and Arg, produced protosta-12,24-dien-3beta-ol, lanosterol, and parkeol. Overall, Trp232 plays a catalytic role in the influence of rearrangement process and determination of deprotonation position but does not involve intervention in the cyclization steps.

Fig (Ficus carica L.) leaves are produced each year and often disposed, resulting in a waste of resources. Fig waste leaves are rich in flavonoids, which have strong antioxidant activity; however, the variety and chemical structure of antioxidants in fig leaves have not been reported in detail. To take full advantage of fig waste leaves, antioxidant capacity of different extracts (petroleum ether, ethyl acetate, and water) was evaluated by 1, 1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS), and ferric-ion-reducing antioxidant power (FRAP) methods. The results showed that flavonoids in ethyl acetate extraction had the highest content (83.92 ± 0.01 mg/g), maximum DPPH scavenging activity (IC50 0.54 mg/mL), highest ABTS scavenging rate (80.28%), and FRAP (3.46 mmol/g). Furthermore, an HPLC-QTOF-MS/MS-DPPH method was developed to identify 11 flavonoids in fig waste leaves. This rapid and efficient method can not only be used for screening the antioxidant components in fig waste leaves, but also can be combined with mass spectrometry to identify the compounds with antioxidant capacity. There are three flavonoids with significant antioxidant capacity, which are 3-O-(rhamnopyranosyl-glucopyranosyl)-7-O-(glucopyranosyl)-quercetin, isoschaftoside, and rutin. The results confirmed that fig waste leaves contain a variety of antioxidant components, which contributed to increase the value of fig waste leaves as antioxidants.

Fig tree cultivation land resources are not fully utilized and introducing them into sustainable medicinal agroforestry systems can effectively achieve resource protection and reuse. Laboratory and pot experiments were applied to study the allelopathic effects of fig tree (Ficus carica L.) leaf aqueous extract at five mass concentrations of 8.3, 10.0, 12.5, 16.7, and 25.0 g/L on the morphological and physiological indexes of mint (Mentha haplocalyx Briq.), dandelion (Taraxacum mongolicum Hand.-Mazz.), and woad (Isatis indigotica Fort.). The results showed that mint had the best seed germination rate. The leaf aqueous extract at lower concentrations had a strong promoting effect on the biomass and photosynthetic parameters of mint, dandelion, and woad. With the increase in leaf aqueous extract concentration, the superoxide dismutase, peroxidase, and catalase activity of mint, dandelion, and woad increased initially and then decreased, but the malondialdehyde content increased. The synthetic allelopathic indexes of the three medicinal plants were in the following order: mint > woad > dandelion. Both the low and medium concentration extracts (8.3 g/L–12.5 g/L) showed an obvious promoting effect, while high concentrations exhibited distinct inhibiting effects. In conclusion, mint is the most suitable medicinal plant to be interplanted with fig trees for introduction into medicinal agroforestry systems.

The velvetleaf (Abutilon theophrasti Medik.) is a strong and competitive weed in fields that inhibits the growth of crops. Reports have suggested that allelopathy is one of the reasons for this inhibition; however, the mechanism of this allelopathy remains unclear. In this study, velvetleaf powder/extracts were shown to inhibit seed germination, growth and yield in maize, wheat and soybean through petri dish, pot and field control experiments. We observed a concentration-dependent inhibition of the seed germination rate for all three crops. The root tip structure changed significantly and the embryo even died when irrigated with a high concentration of the extract (10 mg·mL−1). After adding velvetleaf powder, the malondialdehyde (MDA) content in crop seedlings was dose-dependent, and the superoxide dismutase (SOD) activity of maize, wheat and soybean showed the maximum values under treatment with 1.25, 5 and 5 mg·cm−3, respectively. The activity of peroxidase (POD) showed the highest value under the 5 mg·cm−3 treatment in maize and wheat seedlings and under 10 mg·cm−3 treatment in soybean seedlings. However, sugar, protein content and root activity in all three crops was the lowest under the 10 mg·cm−3 treatment. Therefore, velvetleaf may decrease the productivity of three crops by changing the antioxidant enzyme activities, root system activities and root tip structures.

No abstract