Gas Chromatographic-Mass Spectrometric Analysis, Antibacterial, Antioxidant and Antiproliferative Activities of the Needle Essential Oil of Abies pindrow growing wild in Kashmir, India

Antioxidant Activity of Essential Oils from Pinaceae Species

“…For instance, spectrophotometric measurements are usually carried out after maintaining the prepared mixture of sample and free radicals (DPPH) for a particular duration. Although most often this duration was 30 min (e.g., [ 39 , 40 , 43 , 44 , 45 ]), in various published papers, it varied considerably: 10 min [ 46 ], 20 min [ 47 , 48 , 49 , 50 , 51 ], 25 min [ 52 ], 40 min [ 53 ], 50 min [ 42 ], 60 min [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ], or 70 min [ 62 ]. Very often, the period after which the spectrophotometric measurements were performed was not mentioned (e.g., [ 63 , 64 , 65 ]).…”

“…A variety of positive controls were used: ascorbic acid [ 47 , 52 , 58 , 70 , 71 , 72 , 73 , 74 ], alpha-tocopherol [ 45 , 52 , 64 , 75 , 76 , 77 ], BHA [ 45 , 55 , 74 , 78 , 79 ], BHT [ 42 , 44 , 45 , 54 , 58 , 67 , 76 , 78 , 80 , 81 ], beta-caryophyllene [ 64 ], caryophyllene oxide [ 64 ], quercetin [ 42 ], tannic acid [ 82 ], gallic acid [ 60 , 83 ], thymol [ 84 ], and even Thymus vulgaris essential oil [ 62 ].…”

“…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 ]. …”

“…The results between different labs are often not negligible for the same comparator using the same endpoint. For ascorbic acid using the DPPH method, for instance, the following IC 50 values have been reported (we converted mg/mL to μg/mL): 1.75 ± 0.69 μg/mL [ 70 ], 2.0 ± 0.13 [ 85 ], 3.27 μg/mL [ 47 ], 5.0 ± 0.4 μg/mL [ 101 ], 6.25 μg/mL [ 71 ], 11.5 μg/mL [ 72 ], 19.0 ± 1.1 μg/mL [ 69 ], 22.61 ± 1.08 [ 97 ], 40 ± 110 μg/mL [ 73 ], 46.54 ± 3.64 μg/mL [ 52 ], 53.24 ± 3.25 [ 59 ], 54 μg/mL [ 74 ], and 84 ± 63 μg/mL [ 99 ]. How do we use such a variety of values spanning almost two orders of magnitude?…”

“…For instance, among the leaf EOs from four Abies species for which antioxidant data were available, three of them ( Abies pindrow (Royle ex. D.Don) Royle [ 47 ], Abies alba Mill. [ 85 ], Abies balsamea (L.) Mill.…”