Table 1 Fitting statistics, analysis of variance and regression coefficients of the models constructed for each specialised metabolite of H. physodes. Variable coded: X₁: menthol/camphor ratio; X₂: liquid/solid ratio (volume/mass); X₃: temperature of extraction (°C); X₄: time of extraction (min).

Term	Coefficient estimate	p-value	Term	Coefficient estimate	p-value
Intercept	28.72		Intercept	37.05
\(\:{X}_{1}\)	− 0.0529	0.9626	\(\:{X}_{1}\)	− 1.53	0.1739
\(\:{X}_{2}\)	8.86	< 0.0001	\(\:{X}_{2}\)	2.14	0.1006
\(\:{X}_{3}\)	1.61	0.1814	\(\:{X}_{3}\)	− 0.0489	0.9667
\(\:{X}_{4}\)	2.68	0.0188	\(\:{X}_{4}\)	4.66	0.0005
\(\:{\text{X}}_{2}^{2}\)	− 3.87	0.0270	\(\:{X}_{2}{X}_{3}\)	5.82	0.0009
			\(\:{X}_{3}{X}_{4}\)	− 3.04	0.0597
Model		< 0.0001	Model		< 0.0001
Lack of fit		0.3149	Lack of fit		0.4545

Term	Coefficient estimate	p-value	Term	Coefficient estimate	p-value
Intercept	18.77		Intercept	8.37
\(\:{X}_{1}\)	− 0.1615	0.8375	\(\:{X}_{1}\)	0.2526	0.5214
\(\:{X}_{2}\)	6.25	< 0.0001	\(\:{X}_{2}\)	2.64	< 0.0001
\(\:{X}_{3}\)	1.33	0.1143	\(\:{X}_{3}\)	0.6491	0.1299
\(\:{X}_{4}\)	3.16	0.0008	\(\:{X}_{4}\)	2.20	< 0.0001
\(\:{X}_{3}{X}_{4}\)	− 2.16	0.0546	\(\:{X}_{3}{X}_{4}\)	− 1.29	0.0234
			\(\:{\text{X}}_{3}^{2}\)	− 1.04	0.0797
Model		< 0.0001	Model		< 0.0001
Lack of fit		0.537	Lack of fit		0.6752

Term	Coefficient estimate	p-value	Term	Coefficient estimate	p-value
Intercept	2.11		Intercept	84.33
\(\:{X}_{1}\)	0.1696	0.1786	\(\:{X}_{1}\)	− 1.72	0.5634
\(\:{X}_{2}\)	0.8749	< 0.0001	\(\:{X}_{2}\)	23.22	< 0.0001
\(\:{X}_{3}\)	0.1674	0.1983	\(\:{X}_{3}\)	3.12	0.3221
\(\:{X}_{4}\)	0.5128	0.0001	\(\:{X}_{4}\)	13.94	0.0001
			\(\:{X}_{3}{X}_{4}\)	− 9.06	0.0343
Model		< 0.0001	Model		< 0.0001
Lack of fit		0.4449	Lack of fit		0.5643

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