Variation of Essential Oil Composition, Antioxidant and Anticholinesterase Activities between Pinus halepensis Mill. Plant Organs

Antioxidant Activity of Essential Oils from Pinaceae Species

“…Further differences were found for the endpoint used to report the results of the DPPH test. Whereas in many cases this was based on an IC 50 value (e.g., [ 47 , 54 , 69 ]), despite using a synonym name (such as EC50—half maximal effective concentration [ 41 , 79 ], RC50—50% reduction concentration [ 85 ], or SC50—50% scavenging concentration [ 42 ]), in other cases, different endpoints were used as follows: Percentage of DPPH inhibition measured for a single sample prepared in a wide variety of ways (i.e., very different concentrations, e.g., 5 mg of essential oil diluted to 5 mL with ethanol, treated with 250 µL of DPPH in methanol (5.07 × 10 −4 M) [ 55 ], 100 µL of essential oil mixed with 3.9 mL of DPPH solution [ 86 ], 50 μL/mL [ 87 ], or even without details on the way the sample was processed but referencing a published source without clear statement whether identical amounts were used [ 53 , 82 , 88 ]); Percentage of DPPH inhibition measured on three to five different amounts/concentrations of essential oil with no IC 50 estimation [ 72 , 78 , 89 ]; Equivalents to certain antioxidant substances expressed as mg per gram of essential oil (hydroxytoluene equivalent; ascorbic acid equivalent; Trolox equivalent) [ 90 , 91 ], μM equivalents per gram of essential oil [ 51 ], mM equivalents per ml [ 48 ] or per liter of essential oil [ 56 ], or μg of equivalents per ml of essential oil [ 92 ]. …”

“…Equivalents to certain antioxidant substances expressed as mg per gram of essential oil (hydroxytoluene equivalent; ascorbic acid equivalent; Trolox equivalent) [ 90 , 91 ], μM equivalents per gram of essential oil [ 51 ], mM equivalents per ml [ 48 ] or per liter of essential oil [ 56 ], or μg of equivalents per ml of essential oil [ 92 ].…”

“…Similar wide variability in performing and reporting results was also found concerning the ABTS method. For instance, results were reported as IC 50 (in μg/mL [ 39 ], mg/mL [ 64 ], or % [ 94 ]), TEAC (Trolox equivalent antioxidant capacity) (mEq Trolox/g EO [ 91 ], μmol TE/g DW [ 40 , 48 ]), the percentage of scavenging activity at defined concentrations [ 89 ], and ascorbic acid equivalent/g [ 74 ]. There are also differences in how the method was put into practice.…”

“…Various experimenters reported waiting for 12–16 h before use [ 40 , 74 , 89 , 96 ], 14–16 h [ 52 ], 14 h [ 71 ], 16 h [ 64 , 81 , 95 , 97 ], or “one day in advance” [ 48 ]. Absorbance measurement was carried out after 3 min [ 52 ], 5 min [ 91 ], 6 min [ 40 , 48 , 64 , 70 , 71 , 81 , 89 , 95 , 96 , 97 ], 7 min [ 71 ], or 30 min [ 74 , 94 ]. The solution was diluted to an appropriate absorbance level with pure water [ 70 , 74 , 97 ] or methanol [ 52 , 71 ].…”

“…The solution was diluted to an appropriate absorbance level with pure water [ 70 , 74 , 97 ] or methanol [ 52 , 71 ]. For DPPH, various substances were used as positive controls: ascorbic acid [ 52 , 70 , 71 , 94 , 97 ], Trolox [ 39 , 40 , 48 , 51 , 97 ], alpha-tocopherol [ 52 , 64 ], BHT [ 81 ], BHA [ 74 , 94 ], beta-caryophyllene [ 64 ], and caryophyllene oxide [ 64 ], and in multiple cases, no comparator was employed [ 89 , 91 , 95 , 96 ]. Although active controls were mentioned as used, their antioxidant values were sometimes not reported [ 94 ], and are the equivalent of no control.…”