Table 4.

Stability of the 12 investigated compounds.

No.	Compound	2 h	4 h	8 h	12 h	24 h
1	Fumaric acid	94.36%	92.12%	91.12%	91.11%	89.56%
2	Caffeic acid	95.12%	94.16%	93.45%	92.42%	90.12%
3	Catalpol	93.26%	92.15%	91.89%	91.62%	91.02%
4	Aucubin	95.62%	94.26%	93.45%	92.47%	92.41%
5	p-Coumaric acid	95.19%	95.13%	94.16%	93.28%	92.52%
6	Ferulic acid	95.47%	94.13%	93.56%	92.45%	91.44%
7	Harpagide	94.82%	93.46%	93.48%	92.89%	90.46%
8	Cinnamic acid	94.56%	93.74%	92.46%	91.85%	90.76%
9	p-Methoxycinnamic acid	95.05%	94.85%	94.01%	93.43%	92.55%
10	Verbascoside	95.22%	94.56%	94.11%	93.84%	91.09%
11	Angoroside C	95.62%	94.51%	93.56%	93.01%	91.95%
12	Harpagoside	94.85%	94.02%	93.45%	91.96%	90.41%