TABLE 4

Summary of the mechanistic data for permeability of phenolic acids across Caco-2 monolayers and the calculated transcellular permeability predictions

Permeability in all mechanistic studies was investigated by measuring the transfer of compound (500 μM) from donor (pH 7.4) to receiver (pH 7.4) compartment after a 1-h incubation with confluent monolayers (n = 3) at 37°C in a humidified 5% CO₂ atmosphere. Values are mean P_app ± S.D.

Compound	Log D_{pH 7.4}	Mechanistic Studies					Dominant Absorption Characteristic
		Caco-2 permeability P_app		Efflux Ratio (P_app B→A/P_app A→B)	Variable TEER Resistance P_app			Evaluation of the Model Prediction
		A→B	B→A	Efflux Ratio (P_app B→A/P_app A→B)	High	Low		Log P_app	Log P_app^trans	Residual Error
		(×10⁻⁶) cm/s			(× 10⁻⁶) cm/s
Caffeic acid	−1.35	1.4 ± 0.1	1.7 ± 0.1	1.2	—^a		Paracellular	−5.84 ± 0.1	−5.03	−0.8
5-O-CQA	−3.05	0.38 ± 0.1	0.33 ± 0.1	0.9	0.25 ± 0.1	0.77 ± 0.1^†	Paracellular	−6.42 ± 0.2	−11	4.6
3,5-DiCQA	−1.04	0.14 ± 0.02	0.72 ± 0.1	5.1	0.05 ± 0.01^*	0.68 ± 0.1^†	Efflux	−6.85 ± 0.1	−6.34	−0.5
Ferulic acid	−1.19	10.0 ± 0.2	10.2 ± 1.1	1	10.8 ± 0.6	11.2 ± 0.8	Transcellular	−4.98 ± 0.1	−5.01	0.03
5-O-FQA	−2.79	0.25 ± 0.1	0.28 ± 0.1	1.1	0.31 ± 0.1	1.7 ± 0.4^†	Paracellular	−6.60 ± 0.2	−10.6	4
DMCIN	−1.01	19.9 ± 0.1	21.7 ± 0.7	1.1	N.D.	N.D.	Transcellular	−4.7 ± 0.003	−4.93	0.2

DMCIN, 3,4-dimethoxycinnamic acid; N.D., not determined.
↵* Statistically significant difference (P < 0.05) between mean experimental Caco-2 permeability (A→B) and permeability at high TEER.
↵† Statistically significant difference (P < 0.05) between mean experimental Caco-2 permeability (A→B) and permeability at low TEER.
—, data could not be translated from reference; see Konishi and Kobayashi (2004) for details.