Isolation, structure modification, and anti-rheumatoid arthritis activity of isopimarane-type diterpenoids from Orthosiphon aristatus

Figures & data

Figure 1. Chemical structures of diterpenoids 1 − 8 isolated from O. aristatus.

Figure 2. ¹H-¹H COSY (bold lines), HMBC (blue arrows), and NOESY (dash line arrows) correlations of compound 1.

Table 1. ¹H and ¹³C NMR spectral data (500 MHz for ¹H and 125 MHz for ¹³C in methanol-d₄) of compound 1 (δ in ppm, J in Hz).

No	δH	δC
1	4.53, dd (3.0, 1.5)	76.8
2	3.99, t (3.0)	65.9
3	3.51, dd (3.0, 1.5)	81.9
4		39.1
5	2.29, dd (12.4, 2.7)	33.1
6	α 1.88-1.84, m	27.5
	β 1.83-1.77, m
7	4.74, dd (4.3, 1.7)	62.5
8		143.7
9		157.0
10		47.0
11		200.4
12	α 3.18, d (14.0)	51.1
	β 2.50, d (14.0)
13		51.7
14		201.9
15	6.16, dd (17.4, 10.8)	142.1
16	a 5.13, d (10.8)	114.8
	b 5.10, d (17.4)
17	1.24, s	24.5
18	1.08, s	28.8
19	0.94, s	21.8
20	1.27, s	19.0

Figure 3. Experimental ECD curve of compound 1 (solid red line), and M062X/TZVP//B3LYP/6-31G(d) calculated ECD spectra of 1 R,2S,3S,5S,7R,10S,13R-1 (solid black line) and 1S,2R,3R,5R,7S,10R,13S-1 (dash black line).

Scheme 1. Structures and reactions in modifications of orthosiphol K (4).^a

^a Reagents and conditions: (a) Cs₂CO₃, DMF, 3-OMePhCH₂Br, 80 °C, reflux; (b) Cs₂CO₃, DMF, CH₃CH₂Br, 80 °C, reflux; (c) Propanoic acid, DMAP, EDCI, CH₂Cl₂, 0-25 °C,6h; (d) Cs₂CO₃, DMF, MeI, r.t., 24h; (e) Jones reagent, acetone, 0-25 °C, 1.5-2h; (f) NH₄OH/MeOH, 110 °C, reflux, 0.5-1h.

Figure 4. Cytokine release levels in TNF-α-induced MH7A cell model. (A) IL-1β release levels. (B) IL-6 release levels (^####p < 0.0001, vs. control group; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, vs. model group).

Figure 5. Effect of compound 10 on TNF-α-induced IκBα, NF-κB p65, COX-2, and NLRP3 protein expression in MH7A cells. (A) Western blot analysis and (B) Quantified protein expression levels. (^#p < 0.05, ^##p < 0.01, ^####p < 0.0001, vs control group; *p < 0.05, ***p < 0.001, ****p < 0.0001, vs. model group).