## 3 Results and Discussion  
### Acetylcholinesteraseerase Inhibitory Activity  
Acetylcholinesteraseerase (AChE) is the enzyme that serves to break down acetylcholine (ACh) into acetate and choline, and acetylcholine deficiency is correlated with the severity of AD, the most common type of dementia [54]. The inhibition of AChE by natural compounds will induce a high level of ACh in the cholinergic synapses, which enhances its bioavailability and thus prolongs the duration of the neurotransmitter action within the brain [23, 55]. In this study, nine compounds, i.e., eight terpenoids (**1**), (**2**), (**4**), (**5**), (**6**), (**7**), (**8**) and (**9**) and one flavonoid (**3**), were isolated from three African mistletoes (Loranthaceae), and the AChE inhibitory activity of the crude extracts and the isolated compounds was investigated. We found that all crude extracts and six isolated compounds (**2**, **3**, **5**, **6**, **8** and **9**) had a concentration-dependent inhibitory effect on AChE (Figure 2). After the IC\({}_{50}\) values of active samples were determined by non-regression linear using the software GraphPad Prism 6.0 (see Table 1), it was observed that if compared to eserine (IC\({}_{50}\)=1.23 \(\mu\)g/mL or 4.47 \(\mu\)M) used as the positive control in this study, the crude extracts had weak to moderate inhibitory potential against AChE, with the seed extract of _T. bangwensis_ (MSTB) having the highest activity (IC\({}_{50}\) of 48.97 \(\mu\)g/mL). The compound 3\(\beta\)-acetoxy-11,12-epoxytaraxerol (**9**) isolated from this active extract (MSTB) was the most potent, with an IC\({}_{50}\) value of 6.92 \(\mu\)g/mL (13.89 \(\mu\)M). Previous studies have reported theACHE inhibitory activity of taraxerol isolated from _Clitoria tenatea_ with an IC\({}_{50}\) value of 69 \(\mu\)M [56] or from the twigs of _Vaccinium oldhami_ with an IC\({}_{50}\) value of 33.6 \(\mu\)g/mL (79 \(\mu\)M) [57]. Therefore, the current study identified a new taraxerol derivative, namely, 3\(\beta\)-acetoxy-11,12-epoxytaraxerol (**9**), as being more potent than taraxerol against AChE, which warrants further investigations on structure-activity relationships with taraxerol derivatives. Structural optimization is always more ideal for drug chemistry concepts that explore potency based on their composition and later inspire the development of a number of lead candidates [53]. Three other compounds, 3-O-\(\beta\)-D-glucopyranosyl-28-hydroxy-\(\alpha\)-amyrin (**2**), apigenin- 8-C-\(\beta\)-D-glucopyranoside (**3**) and globimetulin C (**6**), also had good AChE inhibitory effect, with IC\({}_{50}\) values of 18.63 \(\mu\)g/mL (30.84 \(\mu\)M), 25.06 \(\mu\)g/mL (57.81 \(\mu\)M) and 24.64 \(\mu\)g/mL (36.18 \(\mu\)M), respectively. It is therefore clear that the active compounds (**2**), (**3**), (**5**), (**6**), (**8**) and (**9**) were responsible for the efficacy of their respective plant extracts against AChE, which further confirmed the medicinal usage of _P. capitata, T. bangwensis_ and _G. dinklagei_ against brain dysfunction related diseases as previously reported in an ethnopharmacology survey [5]. Additionally, this study also revealed an increase in the AChE inhibitory activity after the purification of more active compounds from bioactive extracts although we did not use a bioassay-guided method for their isolation. Despite the fact that most of the potent AChEIs from plants are alkaloids, several non-alkaloidal compounds including terpenoids, flavonoids or phenolic compounds have been identified as efficient against AChE [58]. In this study, we report one flavonoid (**3**) and five terpenoids, (**2**), (**5**), (**6**), (**8**) and (**9**), which are identified for the first time as having promising AChE inhibitory potential. Nitric Oxide Production Inhibitory Activity and Cytotoxic Effect on LPS-Stimulated RAW 264.7 Macrophages  
Nitric oxide (NO) plays an important role in inflammation, and its overproduction within the central nervous system is associated with the pathogenesis of AD [27].